I think the liner you saw is probably for the FGR, not FGP. If so, it is an entirely different engine with no parts in common.

To be honest, unless you get lucky, it will be hard to find a P/L set for your FP.60 (the liner and piston are a matched set and not sold separately). You may have to buy a used engine for the parts. But, maybe someone here has a spare set they'll sell.

Here's one: 320359014306

Good luck.

David