I am looking for a back glass for my 91 Toyota Corolla All Trac.  I have tried the wrecking yards and glass companies but not much luck.  Any help would be great.  

What is your geographical area?

http://www.car-part.com/ Although for glass this is probably not a very good option, due to shipping hazards and cost.

Local glass shops will be your best bet, or those within driving distance. If you can find an old one ran by an older person who has been in the business a long time, they often are able to make custom pieces of glass very easily in my past experience.

I live in Provo Utah and I have checked the local wrecking yards, glass companies and dealers.  They have a couple back east but would cost a fortune to get out here.  I am really looking for an affordable used one.

Ok, how about these? http://www.searchtempest.com/ or http://craiglook.com/ and finally http://www.allofcraigs.com/

I've seen some people listing these All Tracs as parts cars in Colorado. when I was searching for my bumper.

Those are some great sites!!!  Thanks and I'll keep looking.  

I have back glass available but I live in Washington state. If you pay shipping I'll sell it to you $40.

As of today there are two sellers on eBay peddling back glass. One guy wants $300 for it, and it has no hole for the rear wiper but does have all the decals, etc.