ruthven:
If EBay doesn't work out, you could try
www.oldsoftware.com , they may have some 520's left (I bought one of mine from there)
I second the vote for a hard drive for your 500. Sadly, as with a lot of Amiga hardware, they aren't cheap.
Most hard drive interfaces for the 500 will be SCSI, make sure you can hook up additional SCSI devices, if needed.
I miss my A500 .... :cry:
It had '030/50Mhz, 32MB RAM, 1GB HDD, Zip drive, DCTV, Epson Stylus Photo ... not too bad for a 500 ....