I have recently found that USB flash drives with both a USB port and an OTG microUSB male are within a few percent of an ordinary flash drive.
I ended up getting the Memorex Dual Micro TravelDrive 64 GB, I imagine the other OTG flash drives will be of similar compatibility.
The Memorex Dual has a hole on back for a neck strap or a ring for keychain.
The flash drive is well protected and in a reasonably tough case. The normal USB jacks into a cap/microUSB adapter. The adapter has a pull over protective cap which has a hole in the end, retracted you can jack into your phone's microUSB port, pull to extend and it clicks over a detent about 1mm past the end of the microUSB's end. I worry that in regular use the microUSB could attract a static electricity spark through the hole in the protective cap, this is a problem as the microUSB adapter is plugged in to the USB flash drive in the closed configuration. I also worry that pocket debris could end up clogging the microUSB tip. Unfortunately the Memorex Dual design only has room to allow the connected flash drive to use the tough and permanently connected OTG adapter so you would still need an adapter cable for other USB stuff that you might carry.
With USB Mode app installed it is easy to go into the status area and switch to USB host mode and automatically mount and unmount the flash drive when needed. The drive appears in File Manager after a few seconds, rarely the process requires a repeat to mount properly and then it is as accessible as your SD card or MyDocs.
The main concern is that being a rigid connect the N900's fragile microUSB port is at risk especially considering the flash drive is a rigid lever inserted into the port, use the utmost caution.
I imagine a similar compatibility report would come from any of the USB OTG compatible flash drives, the Memorex seemed tough enough and was the best price on the day I was buying. I only wish I could use the USB-microUSB adapter with other USB devices and that the protective cap were of a more secure design.
http://www.memorex.com/en/usb-flash-...o-traveldrive/

nice
my freind got a usb flash drive 32gb probably chineese very small with a little retrackable cable with micro usb built in and that works nice on my n900
no fuss super convinent