Break-Free CLP, you can get it almost anywhere. btw - it's what Glock uses themselves.
They use Break-Free CLP and if there is a lot of fouling, they use Gun Scrubber.
As for where to get these products, almost anywhere. Most of the big stores carry Break-Free CLP, even Walmart carries it. Bass Pro, Cabellas, etc., should all have it. Gun Scrubber might be a little harder to find, but again the big stores have it, it's by Birchwood Casey.