How can I fix a stripped hole in an aluminum piece?
Depends on the size of the screw and how much material you have to work with. If this is a clamp bolt, cheap tripods use screws going directly into the casting. Quality units either use a captured nut, Nyloc nut and eccentric toggle or a tee-head bolt with threaded knob.

If this is a plate with a fair amount of metal surrounding the hole and it's deep enough, I would get a Heli-Coil kit. With this kit, you drill the hole oversize with the supplied drill, use the supplied tap and then the tool to install the helical insert.



Another thread repair is Keensert which, if you have yet more metal because it's a larger device, a locking insert that doesn't require delicate use of Red Loctite to keep it in place.



All the above probably are not recommended in the case that the threaded hole is in a casting that doesn't have spare metal, so the previous recommendations of drilling oversize and tapping for a larger bolt might be the best. Which might not be a solution if the threads are common photography standard attachments between devices.