The main reason I went with the Malossi 7 port QT50 cylinder was mainly do to ease of install and a really good deal that I got on it. A guy had bought it for his kids pw50, but ended up stepping up to a cobra dirtbike before install, so I was able to pick it up for a steal. Plans to send it over to MCE a local 2 stroke porter that is very well known in the kawi tipple 2 stroke drag racing.
I haven't ruled out buying a different top end and have had my eye on a few that I believe with some case welding and machining. I could for sure make fit. As mentioned before, Changing out the con rod to a 12mm pin with same stroke would be ideal and open options up tremendously.
Here is 1 kit I dont know much about, but may be a descent option? also looked at some liquid Jog and zuma cylinders I think could possibly work as well.