Unless your 2091 has version 7 ROMS, that 4GB drive won't work either. I had a couple of 2GB drives salvaged from a Sun box that wouldn't work either. I couldn't even get them to work partitioned as 1GB drives. The 500MB drive from a mac external drive worked great.
IDE cards have been made... I don't see any still available either, at least on a quick search.
This is not entirely factual. An older rev rom a2091 can use 4gb drives from what iirc.
