I’ve contacted Retroflag to see if they have spare silicon pads. In the meantime, I’ve rotated the pad around 180 degrees so at least games that only use the bottom two buttons are playable.
Thanks for the tip. That product looks like it’s intended for the carbon contacts themselves. Do you know if it help with the torn silicone part (the contacts on my pad are fine)?
And just to follow up, the product Liam recommended is more for the repair of the carbon pads, but you could probably use any flexible silicone compatible glue to get by in the short term. A little bit RTV-silicone gasket goo (available from any automotive store) applied carefully with a needle or toothpick would probably work ok as a quick fix.