Mission: To find a t-shirt with Joe Btfsplk on it for the wife of Mr. Reeves
I also could not find an image of high enough resolution to use on a T-shirt. T-shirt graphics don't have to be as high in resolution as printed products but they still need to be higher than your run-of-the-mill Web artwork.
I checked all of the sites that sell Li'l Abner merchandise, but they generally concentrate on comic strips, books, buttons, etc - not many sell T-shirts (and I couldn't find anything with Joe's image on it).
My suggestion: Purchase a book, like this one, with Joe's image in it. You can then scan the image and put it on a T-shirt free of charge at many sites. I will be glad to help you, if need be. (But I can't create the product and sell it to you because it would go against licensing agreements, copyrights, etc. But if you buy it yourself and make it yourself for only yourself - I think it would be fine.)
So, buy the book. Tear the page out. E-mail me when you get it. I will send you my mailing address. I will scan the artwork in for you and walk you through the process of getting it on a T-shirt.
I never heard from him again. ;)