KLX125 Engine ???

I have a 2004 KLX125L that I blew the motor up on. Snaped the camshaft in 2 pieces. Ive been trying to find a complete engine assembly but not having any luck. Does anyone know where I can find one. I have also been throwing the idea around (which id prefer) of putting in a 250 in it and fabricating everything else up to make it work. Does anyone have an idea of what engine would be the easiest to work with? I know its not going to be a direct bolt up so im gonna be fabricating anyways.

Thanks, Mike