First of all, don't do it; you could end up damaging other parts of the frame. Secondly, you'd spend as much time finding such a thing (if one exists) as you would buying a replacement shock off eBay.

IIRC, eye-to-eye was 6.5 and stroke was 1.5 on most of those FSRs on either side of year 2000. It's still a common-as-water size and shouldn't be difficult to turn up a suitable replacement.