I just bought 3 of these:

http://www.cellphoneshop.net/unusbchkitfo.html

(their "sale" says it ends today ... it says that every day: I think they claim to be on sale so you wont wait to buy, sort of trying to influence an impulse buy)

I got 3 so I can have one at home, one at work, and one in the car (I was buying more for the cable+nokia adapter than for the car charger piece, which is just a cigarette-lighter-to-USB device).

It works just fine (I have a nokia 2865i, so I knew the N800 used the same charger already). In fact, I used one in the car today to charge my phone, and one at work to charge my tablet.

I'm probably going to buy 3 more (2 cables at each location), and then buy one of those dual USB car chargers for use in the car. (if I do, then I'll post again, and offer anyone here to have the single USB chargers, without the cables nor adapters, that came with this: $2+shipping)

Anyway, point is: if you want such a thing, I can endorse that as "it works". At, on the first day at least, neither my phone nor my tablet fried from using it.