Sorry to see the housing break like that. I wonder why it broke, seeing the gears appear to be intact. I've been looking for a 48" tiller too, but they're expensive. Tractor Supply carries 3 point hitch tillers, but the cheapest is about $2200.
I have a neighbor who tills our primary garden, then I redo it with a small electric rototiller a few weeks later (this weekend in my case). I'm not looking forward to it as it's warmed up significantly this week. Anyways, our little electric tiller ran about $120 on Amazon. That might be a temporary, fill-in solution until you either fix your Howard tiller or find a replacement. I have a old-fashioned wheel hoe I could send up, if you want some exercise!