There are some things in the market that tend to see replacement parts come out in droves and even if not in availability, you're bound to find some on Aliexpress. Sadly though the F710 doesn't have replacement pads/sticks as does the Xbox 360. You could source a broken or cheap Logitech F710 controller and swap out the parts you need for your existing controller. In fact you could hand it down to someone who'd like to use it casually while you picked another one up, new ofc.