I'd like to use T.I.E., but I don't have Shivering Isles and it seems that it's required. Do I have any options? Any older versions around anywhere?

Buy SI

If you are having fun with oblivion, then SI is worth it.

So if that is not an option, is it possible to use an older version that does not require SI? What was the last version before SI was required. I am trying to find it, but it's not easy.

Probably version 1.26? Good luck finding it though since Veritas has made it very clear all future TIE work requires SI and all the old copies are gone.

SI isn't exactly expensive - you could get it as part of a GOTY package in most places for $20.