10 usually comes with 11 pressed in. You can get 6 with 7 pressed in, but I haven't seen it come with 15.

can't remember where I got them from, but it was one of these:
ECS tuning
Bimmerspecialists
Bavarian Autosport
or carpartswholesale.com (careful with these guys, they like to tell you items are in stock and then refund you a week later cause they don't have it)

Sorry I can't remember which one it was