I'm currently resurrecting a YS 60 standard stroke and can't find that little check valve for the pressure line... does anyone know if it is possible to use a generic check valve from the local hobby shop for this purpose? Does it have to be the YS version for some special high-tech reason?

You are better off with the YS valve but the answer to your question is yes. Perry (perry pumps) makes one, I believe Durbro makes one (or did), and a few others. Stay away from the plastic ones you will find. If in a bind though... they will get you through. Just do not use them long term.