I've read about using strobes, but I don't know how much of an investment they would be. I'm guessing that you would be better off buying the 50mm lens since that would be considerably cheaper.

I'm guessing you would need to get some radio slaves so you can trigger the strobes remotely plus the lights themselves. I don't know what portable strobes go for, but if they're anything like studio lights, the cost would be fairly high.