Presumably your method for getting into sonic welded cases differs from mine - which does not result in a case that goes back together.
I was looking to get my Compaq M300 battery replaced and found them. But not many other places doing this. Doing some research, I found a lot of complaints about them - generally about turnaround time. I tried calling them a couple of times but at the time just got a message. Bottom line - I think there is a market for this.
Is there a university near you? If so, lots of laptops. Put an ad in the school newspaper, online, whatever.
As to photo gear, I'd say you're best market is equipment where new packs are no longer available. I.E. if I don't get the battery pack rebuilt, the equipment is worthless.
As to drills, it might be hard to justify 2 way shipping cost for a battery. Batteries Plus rebuilds packs (or at least used to); you might want to look into their pricing for guidance.
Google will get you to a vendor for almost any battery. But it won't weld the tabs and won't open and reseal sonic welded cases.