A little more investigating has turned up one that was known to work.

The Adtron Accent.

http://www.adtron.com/products/Aspc.html

Take a look at the manual that is at the bottom of the page.

I found it while browsing through the Low End Mac Duo List. Someone with a 2300 was using it. I'm not sure what operating system they were running.

I have no idea whether or not you can boot from it.