NM&R Chatroll. The only Stampede I've owned served as the platform for my LTX DMR and in general I like the 18 dart straight Clips. I prefer them to the 18 dart drum clips that the Alpha Trooper comes with (now also available on it's own @ Target). A Voltage Mod and a spring from Orange Mod Works could really make this a nice blaster for someone.
If you can't seem to find these in your stores, go to Toys R Us' website and order them off there. It's free shipping too, so it's the same price you would pay for getting it at the store without that sense of "instant gratification". It's likely these won't stay this cheap for long. You can also get these from Wal-Mart for 34 bucks WITH a Bandoleer included! That's an even better value!