Just jumping in here since I was looking at buttons / ball tops earlier for modding my stick.
Seimitsu (LB-39) has the bubble top green / purple / red that might match your Joker theme color.
If you’re looking for translucent Sanwa’s, it’s the LB-35, but as far as I know they don’t have Translucent purple, and the Translucent green doesn’t match the Joker green, at least not the “toxic” green that comes to mind for Joker. You’d probably need to go solid color if you want Sanwa, the solid color LB-35’s for the green / violet / dark red colors.
For translucent buttons it’s either Sanwa OBSC 30 push button or Seimitsu PS14 K (snap in) or Seimitsu PS14 KN (screw in). But the Sanwa OBSC’s don’t have translucent with purple, so you’ll want to go with maybe the Translucent Clear’s (solid button color but with a clear rims) which do have dark red / green. The violet for the Translucent Clear’s is a little pale for Joker purple.
You could also go Seimitsu clear PS14 or Sanwa OBSC Translucent clear buttons and have your colors printed and inserted into the buttons so you get the exact shade you want. Can follow this guide for how to insert the artwork yourself. Alternatively, if you wanted to keep the translucent look, I saw a stick where someone inserted color film into their clear buttons to get just the right hue they wanted while still remaining sort-of translucent.
Places like Focusattack.com, Akihabarashop.jp or Canadianjoysticks.com should carry the stuff you’re looking for if you’re in North America.