I put together a disk image with the latest version of the files you should need to run an Ethernet adapter on a PB 100 for System 7.1.x (with the exception of the actual Ethernet adapter drivers, since those are specific to the Ethernet adapter in question). I've tested all the enclosed files on 7.1.x personally and I know they absolutely work. You can either write the image to disk or mount it using Disk Copy. Either way should work. Hopefully you'll find it useful.

http://www.sendspace.com/file/dl0uum