If I were in your shoes, I'd be looking for a parts motor for that bike, at least to get the cylinder studs. Unfortunately, Suzuki is notorious for dropping parts support as soon as it's legally allowable to do so.. so I doubt that you will be able to order OEM parts. It is worth a try, though.
I would not replace the single broken stud with a generic part. The studs are designed specifically for the required tension, and thermal expansion characteristics of the top end. Uniform expansion / contraction is very important to keeping things true, and preventing gasket failures.