The better solution is to purchase the battery adapter kit from Gossen for around $18. This lets you use 1.5v SR44 batteries in the old Luna-Pro. It is apparantly a ring which both surrounds the smaller silver-oxide cells for fit and steps down the voltage to the correct 1.35v.

I just ordered one from Bogen (Gossen distributor in US). B&H also has them listed on their web site.

Zinc Air batteries also work, but last only a few months of use.