Sorry, but you’re out of luck.
While modern polyester-based strings are promoted as being more "spin-friendly”, they will only help you increase your RPMs of topspin if you swing on the proper path with a lot of speed.
The “snap back” effect from poly strings is real, but only if you swing from low to high quite quickly. Since most of don’t do one or both of these, poly strings won’t help with spin generation and may, in fact, hurt our games: being quite a bit stiffer in most cases, power and comfort are much reduced.
If you want to know, when someone asks me how they can get more spin, my answer is always “lessons”. Strings aren’t the “miracle pill”.