Don't know if you already have a scope? This one says it comes with an adapter so you can use a single, standard AA battery.
PSO-1 Sniper Rifle Scope with SVD side-rail mount
Looks like the jjj takes a 3v (Aim point) style or two 1.5v A76 watch batteries, scroll 1/2 way down.
Dragunov dot net - Chinese NDM-86 Rifle Scope
My Russian Kobra red dots take the 3v CR2325 batt, kinda hard to find, but the local drug store has a large selection and carries them. As a last resort you can always try Kalinka. Kinda pricey but I've had good service from them over the years.
Batteries & Bulbs - Optic Accessories
Good luck with your project, Ken -PS- Welcome to the forum!!!!