This is what I could find. 4200 cover and aftermarket Red Barn 5200 piston. I MAY have a 5200 cylinder, but cannot locate it.
I am really not sure because I have a 5200 runner and a Solo 680 as my 2 big saws (I just gave away my Husky 394 to the Hurricane Helene relief effort) and I try to keep the critical rebuild components on hand, but cannot recall for sure if I ever acquired a 5200 cylinder.
Anyway, let me know if you are interested and I will let you know if I locate the 5200 cylinder.
Good luck and Happy New Year!
P.S. Not trying to steal TLG's thunder - if you two have something worked out go for it! Just wanting to let you know I have a few parts available.