I didnt mod mine as an AK, but there are universal AK handgaurds that would work well. The stock though is a problem, the only stocks out for the MRX are the SOPMOD stock. and the M4 stock. You could try making one, Ive seen an MRX with a wooden stock before. Pretty much drill a hole in a block of wood for the stock tube to fit inside, then shape it out into a stock.
Luckily the magazine sort of resembles a banana clip, if you were going for a stockless AKSu, youd be set.