I don't know if an adapter can in some way make a USB OTG cable non-OTG-compatible. I'm a tad confused about that, since all of my OTG devices (my Nikon D80 camera, my iRiver X5 MP3 player, and now the Nokia N810) came with cables, ostensibly because they're OTG-capable.

Actually, my MP3 player that does USB OTG has a proprietary connected--looks like a mini USB jack but with a different shaped metal housing. So, that's also a hint that these cables are usually included because they're required to use OTG with the device.

Anyway, I initially replied just to say that the N810 comes with a USB cable that (needless to say) fits into the micro USB jack on one end and has a regular, male USB A plug on the other. Getting a female-to-female plug for regular USB A would let you then use any USB A-to-whatever cable instead of finding an adapter for everything.

Or, find an adapter for what you need. It depends on what cables you've got lying around and what you'll be using this for.