Maybe they can just tether two ships together and have them rotate around a common CoG like a bucket swinging around on a string. Wouldn't be that expensive. The radiation I'm not sure, maybe they can create a "safe room" on the ship surrounded by their water reserves.

The tether thing is so simple I'm surprised it wasn't in use decades ago. I think I remember them confirming it being a viable option on Gemini when they tested it being tethered to the test vehicle.