Double Side Textured PEI Sheet 235mmx235mm-FugaCity Dual Sided PEI Build Plate with Spring Steel & Magnetic Sticker for Creality Ender 3 /Ender 3 V2 /Ender 3 S1 /Ender 5 3D Printers,Golden Textured

I've had to replace my sticker only once so someone else might know better source, but I was only able to find stickers that come with flexplates. For example this one should include one. You could also find one for larger printer and just cut to size after applying it, it's not a difficult job to do but cutting makes it almost bulletproof. What issues are you having with BLTouch clone? Initial setup was bit wonky for me but after that my clone has been working like a charm.