The grips of the older Steyrs are not exactly similar to the new LP10's grip.
I have an LP10 grip on my LP5 co2, and allthough it fits and works, at the top, it does look different. Modern steyr grips should interchange perfectly though. They're 4sale quite regularly on egun.de
Another grip wont affect the balance. Cán affect POI cause you hold it differently.