I'll try to get to the point. For fun, I'm trying to use an Apple PowerBook 5300c (Mac OS 7.5.2) to do some programming, but struggling to get some files on to it. It sounds like CD-ROM isn't an option for the 5300c, and someone recommended I buy an Ethernet expansion card. Assuming they meant PCMCIA, I have no idea which card would actually be compatible. I need to find one that comes with Mac drivers sure enough, but will a Mac OS X driver work on Mac OS 7? Surely not! Any ideas?
That machine takes PCMCIA, but not cardbus. I believe that most compatible cards were 10baseT (certainly the one I had was). During the period when I kept my 190cs (same machine excepting that it was a 68LC040 instead of a PPC) and newer machines with 100baseT, I used a cheap switching hub to prevent it from slowing the rest of the network down.
Two months ago I recycled an external SCSI cd-rom drive that I have for the 190. It should work with any SCSI device once you find a converter for the funny SCSI jack (exception, it had weird termination behavior so you can not use it with arbitrary SCSI strings).
I'd suggest asking around of friends and colleagues that had laptops in that era. PCMCIA 10baseT cards were pretty common, I still have two.
As for drivers Pure Mac used to keep a lot of obsolete software around, or you could try with the manufacturer (for those who are still in business, or where the purchases has kept the old web stuff).