What is wrong with this picture? If for some reason you get a hole in your dryer belt larger then a 10 " x 10" there is no one to sell you a piece large enough to fix it. Your option seems to be buy a new belt. The belt on my dryer is 44' long and will cost $1000.00.
The answer to that question may be that if a belt rips to that point, perhaps it's really old and brittle, and standard thought may be that it's not worth mending (of course, the standard thinkers are not footing the bill)
Have you asked a belt maker if you can buy three feet of belt with no ends (or maybe no side seam either)?
I'll see if I can find an old belt I should have kicking around somewhere. PM or email me some info and I'll send you a hunk if so.