Using non-sun mice on a sparc?

I'm trying to get Sparcstation 1 up and running with Redhat Linux, but I don't have any sun mice. I noticed as the install CD boots it looks for a mouse-systems mouse. I have some other workstation mice around here somewhere, and I think at least some of them were marked mouse-systems. Has anyone managed adapt any other mice for use on a Sparc? I know there are some commercial sun to ps/2 adapter, but $75 is a bit much to spend on an adapter for a $5 computer. I though about using a serial mouse, but porting the PC driver to Sparc is way beyond my current skill level. I could always just buy a sun mouse, but the shipping/currency conversion charges are likely to be more than the cost of the mouse itself. Any ideas appreciated...