No one sells stripper clipped/bandoleered US ammo in any quantity anymore, because Klinton ended the surplussing of guns and ammo in '97, and what little remained is just about gone.  If you look around, you may find someone who has a can or three in his personal collection to sell, but you aren't going to find an ammo vendor with it in quantity.

You can occasionally find British ammo this way (in British bandos), but the ammo itself is usually the stuff they downloaded about 300 fps to cycle in their terrible SA80 rifle.

More rare are Canadian cans loaded onto plastic Thermold stripper clips.

I recommend buying quality ammo and assembling the bandos yourself.  It's probably the only way to get what you want.

Check the www.ammo-oracle.com for more info.

-Troy