Try these:
http://www.curbramps.com/home.html
It's a Canadian company but they have 2 U.S distributors, one in KY and the other in CO. I have the same problem you do, bought 4 of these two years ago (but only use 2) and they cured it. I back into my garage and as long as I pull out / back in slowly, I can go straght in, not at an angle. For the $$$, they're hard to beat.