Clarence Lee still does them. Give him a call.
The helicoil is a special 1/4x32 type. There are some tool specialty stores that sell the kit. But it is expensive as you have to buy a bunch of them.
Besides Clarence Lee, if I remember right, there were a couple of others who did the repair too.

This guy used to advertise that he could repair the stripped glow plug threads too:
http://rcudev.rcuniverse.com/communi...mp;memId=74747