Ahhh, that's not good news, and it means you're going to be looking at a serious expense for a complete new water pump.
Possibly the best source will be CGR Ghinassi, the Italian aftermarket parts manufacturer. If you contact them, they will be able to advise how to acquire one of their pumps, and at what cost.
It will almost certainly cost you many hundreds of dollars to acquire a complete new water pump, as they are a big pump, they're heavy, and they are now hard to find, either new or used.
CGR Ghinassi parts are perfectly interchangeable with the genuine equivalents and provide the highest guarantees of strength and durability
www.ghinassi.com