Gpreston43

Hi, I have bought a Yamaha DT50 MX but it needs a new barrel and piston, the bike in in great condition otherwise, completely original so I have decided it is worth doing, the problem is that the engine is from a Yamaha RX50, and as im sure you know are rare, so you cant get parts for them and you cant get the engines, does anyone on here have any suggestions as to what I could do and what my options are getting this bike back on the road? I am new to this so I don't know what options I have, I have considered a replacement engine but not sure what fits the frame, or any barrels and pistons that would fit the RX50 engine? either 50 or 80 cc. Thanks in advance and any advice would be appreciated, George (photo of the bike attached)