Given that I live in the UK, this may not help. Got it from Halfords, cheap as chips! I just cut it to size. Had a quick look on Amazon and they do lots of “spider web” type accessories but these wouldn’t work, the nearest I found was:
https://www.amazon.com/YESSKO-Anti-S...on%2Bslip&th=1
I found that with my wireless charging pad, the phone would still charge as long as it was within 6mm of the pad so the thickness of the silicone made little difference.