hum-hum-humhum...
well...
found
10 uf microfarad capacitors of which I need 2 ..one for input one for output...
http://www.ebay.ca/itm/10pcs-50v-10u...item338a3baae4

found the .1 uf ceramic capacitor I'd need too...
http://www.ebay.ca/itm/360693274546?...84.m1436.l2649

And I can find plenty of 5v voltage regulators...like...
http://www.ebay.ca/itm/3-x-LM7805-L7...item3a67f15482

But try to find a lm7804 (4v) voltage regulator (small enough) anywhere...? Not so easy...

Of course I am no electronics wiz ....in the slightest...
I do believe I am roughly on the right track...but I'd rather be certain...
ESPECIALLY with wiring stuff up...
I'm more of an explosions, lotsa coloured smoke and ever expanding foam blowing out the doors and windows kinda mad scientist ...
Not really the electrocution-with-the-sparks-and-the-convulsive-uncontrollable-shaking-smoking-and-then-PERSONALLY-exploding-kinda-mad-scientist...

There is a reason why the massively obvious switch is way over on the other side of the room when Igor throws it y'know...

Just buy a Pisen 1400mAh battery. $10 to anywhereintheworld

@endso,
You have at least two options:

1. Use a 5V regulator and wire a diode in series with its output. Silicon diodes have about 0.6 to 1V forward voltage drop, depending on power rating (power diodes have a bigger drop). That should reduce your 5V to just the right level.
   The trouble with this solution is that the drop is non-linear. The stated 0.6 to 1V is the maximum drop, if the current is large enough. For very small currents it may be much less. What is "large enough current" depends on the diode, but as a rough guide, assume ~1mA for low power diodes.
   Better try it with a dummy load before exposing your precious to overvoltage.
2. Use a 3V or less regulator and wire it up to give the desired output. You will need two resistors. Connect them in series. The top end connects to your regulated output, the bottom end to the ground. The middle end now provides a reference voltage somewhere between the two, depending on the relative proportion of the two resistors. Connect the regulator's reference input (the pin that normally goes to the ground) to this middle point and hey presto, your regulated output is raised by the relevant value.

There are of course gazillions of other solutions but these are the simplest.

EDIT:
In case I am expressing myself very clearly, here is a page that is:
http://www.learningaboutelectronics....tage-regulator

@independent - I have a veritable ton of batteries for all my Nxx0's ...
that really isn't the issue....
1-When batteries for the Nxx0 device lines cease to be made what then?...That is the last hurrah for our devices then. They are bound to the batts. just to power them on ..forget even running them 5 minutes let alone a day...we are completely at the mercy of "must-having-the-exact-battery-type" forever otherwise...and it is laughable that 5-10-20 yrs from now I'll be able to find a proper batt to use on ANY of my Nxx0's...However it isn't laughable that I won't be using my Nxx0's in 20 years from now ...I've been using a few of them for what ?...7-8 yrs-ish? .. so far quite happily....what's another 20 yrs to my lovely n800's or n810's?...

-For me...It's also about seeing if I can do this... afterward do a vid showing exactly how to do it easy-peasy ...post it...

-AAAANNNNDDD I get to piss around and make a stupidly high-heat resistant dummy-battery form to house the electo-bits outta deer antler ...that is reason enough right there....

@pichlo
ah! thanks pichlo!
I'm sure you have just given me the 1st two to three years of electrical engineering right there
Ok....I do have a couple projects I need to wrap up 1st...
So...In the new year... February in fact ....
I will be starting down the road to self-determined electocuticide ...
'tween now and then I'll get what materials I need and bone-up on what I need to do...following your advice pichlo...
Come Feb when I start...I'm sure I'll have more questions then...

I pondered this issue with respect to the neo900 - but then looked at eBay etc and see sellers still peddling batteries for phones far older than the n900. And there are other phone models that use the BL-5J, so that should help buy some more time.

But your point stands in principle.

yea...for the n900 it's still got plenty of time...
and I do love the neo for the option of running without battery and simply plugged in...huge plus for me.
but I do feel the weight of years pressing down on the n8x0's ..
and having accessible new battery options can't last forever...
also I'd mess with one of my n800's and one of my n810's 1st...
ever before attempting it with my only n900...

and yea...it is mainly about "being able" to do it at this point...
rather than having no choice but to find an alternative ...yet.
What's the bare-bones of that line again?
something like...
"Heaven is options... Hell is none or only one..." ?
I'd rather have the option than none at all...

Not to mention....
there'll be exciting flames, melting things, explosions, pretty bright flashes and bangs that will make me "oooh" and "aaah" and keep me entertained along the way in the process I'm sure...