To get software you could try to get an old i486 machine with a 5.25" floppy drive (with floppies) and use Linux or DOS running in FAT and write the floppies that way. Or, you could be adventurous and try to get an IDE PCI card and 5.25" floppy combo working on a modern machine (most likely going to need Linux since Windows NT, which what modern Windows runs on, probably dropped that legacy support a while ago).
One final option is: make software for yourself because that's what people did in the 80s, everything was pretty much done by hand and people only bought software if they were incapable of programming or the program was too complicated to hand make.
And one final word, nice find. Those computers are very hackable, look up some old computer magazines from around the same time period, they will give you lots of good hardware and software hacks for it.