Try the 782-5252 (4ga 20', and reasonably priced) or -5251 (2ga 25', but much spendier) at Napa. Probably a lot easier for a store to get than Grote, too. They're 100% copper and have pretty nice clamps.
If Sears still has them, I have blue & black Diehard cables I'm pretty sure are the same as...