depends on how good the welder is. A aluminum shop should be able to do it. only concern is they may have to pre heat the block to get good weld penetration and that would require the removal of all rubber and gaskets and seals most likely.
It could be repaired. I would strip down the motor and bring it to them with both case halves bolted together so that it can self support as it heats and cools. They would most likely preheat so you would want to break it down so as not to cook all bearings and seals.
Thanks. That will have to be sorted out after the season. For now, I will just ride the sled with battery, but no e-start. Took the motor out and fuse, so nothing will fry if I turn the key too far.