Most hardware stores that sell siding sell replacement shingles for your situation.
However, they’re not made of asbestos anymore. The substance is an extreme health hazard and is banned for use in anything made in the U.S. today.
Because of the deadly danger, extreme caution needs to be taken when removing the damaged shingles. Some states may even require special permits be issued before the repair is done. It would be best to check with your municipality before you start the work.