I would either:
Buy a single wheel on e-Bay and toss the broken wheel or
Buy a set of 4 wheels on e-Bay, toss the cracked wheel and sell the remaining 3 wheels singly on e-Bay
Given that wheels and tyres are the only thing that keep me going where I want to go, I wouldn't screw around with repairs and welds. Nor would I try and sell a repaired wheel, because it would devalue the other 3 and make the whole set hard to sell
As the default M-sport wheel there are plenty of MV3s around, so doing the switch above shouldn't be an issue.