You can get secondhand amiga mice on ebay for next to nix. I got a few of them with other things, and as misidentified c64 mice. Never got one of them either :-(
As for the pic burning, if you are determined, you can make a simple interface for peecee that uses the printer port and not much else IIRC. I have a 'proper' PIC burner but it's less than reliable on this temporary PC.
There are also 16x84 burning software/schematics available on aminet.
I've been wanting a PS/2 mouse to amiga interface for a while. Far too many other projects on the go as it is with no time to do any.
