Hi alpine and welcome to AS.
Don't know if you'll ever find that gasket.
You can search this thread and find how Joey sealed up those style tanks with 3M 'body accent' foam tape. I have a PM700 he did and no leaks.
I've also recently used a product called Red-Kote and am very happy with the results.
As far as bar size goes, I've used 18" or 20" in all types of wood. But I don't push these saws very hard, either.
Hi Warped and thanks for the reply. I'll see if I can find the thread you noted. If it wasn't such a narrow gasket, making one out of cork would be a snap. I had a broken fuel line as well but was able to find a replacement that worked from another model number. The fuel filter was different as well but I found a suitable replacement locally. You wouldn't think this was such a big deal to fix, but this leak is driving me nuts. Thanks again for the speedy reply.