who sells the cheapest drilled or slotted or both for a 1999 silverado 4wd z71, I figure I got my use out of these.

I've read somewere that stock rotors are a big ticket item, can't emagine after market (if) available.
Turn your rotors, clean up the calipers, and try a set of NAPA Cermix brake pads, these are hands down some of the best brake pads you can buy, and only 10-20 bucks over stock.

I'll never install wadded up metal (Metalic) brake linings again.

My two cents worth!

-Mike

FYI.. This jsut happened to me 2 days ago. After you replace your rear brake pads, be SURE TO TIGHTEN the caliper bolts to the recommended torque, or either use a slight amount of lock-tite. The bolts on my right rear caliper fell out on a dirt road about 10 miles from town and the caliper cut a nice groove on the inside of the rim.