Can we see a pic of the brake pedal for reference?
I'm not familiar with that particular part.
If it has a folding tip, perhaps a tip from another bike could be adapted, perhaps even a tip from a gear lever as those can be a bit wider and rubberised.
If the tip is steel, perhaps the tip could be extended with some competent welding.
I take it the mod should be reversible when your injury is improved, in which case I would take the pedal off the bike and compare it with bike wrecker stock. If you are extemely lucky then you may find a suitable replacement gathering dust, if not you may find another ZZR600 brake pedal to modify and substitute.
If the stock brake pedal is all steel, that opens up the possibilites somewhat as steel would be easier to weld (for most people) than cast alloy.