Clyde Armory in Athens, GA has an abundance of H&K USP 40 mags in the high capacity variant as well as the standard mags. I am not sure about the compact, but I garuntee they will do what they can to help you. You can find them on the web at policeguns.com. Kevin is very into customer service and I have purchased a CZ P06 and an FNP 40 DASA from him. They are a class III dealer and have an amazing selection of unique items from H&K MP5's (real ones) to supressed Beretta 92FS with a Knight Suppressor. Their phone number is (706) 549-1842. Don't work there, not advertising, just a very happy customer. Another source might be Gunclip Depot @ gunclips.net. That's where I found my spare Cougar mags for a great price. Lots of mags there.