There are NiMH ‘C’ and ‘D’ sized rechargeables.
Tenergy Centura are what I found recommended when I was looking for them. They’re low self discharge and thus able to sit in a flashlight longer and maintain more charge.
These will require a charger that can charge NiMH batteries.
If you have experience with soldering I strongly suggest checking this out. I had a blast working on mine.