generic engine for 6x4 Gator???

Hey all, My son picked up a 90's something Gator, we new engine was shot..but didn't know what exactly was wrong. Pulled it out, and sure enough a HOLE in the crank case. Possibly weldable?? I don't know. Could give it a shot.

Otherwise, I know these Kawasaki's FD620d's are hard to come buy AND super expensive.

Was wondering if anyone would know a close equivalent engine that may be fairly "drop in" ready to replace the Kawasaki, and be cheaper?

Any help or tips would be great.

Thanks