I have an older Brembo rear caliper that works with the thin floating rotor (typically found on Trackmagic karts). I’m looking for either the spacer to enable it to accept a wider rotor or the entire Brembo caliper with the spacer installed. I should point out that this is the larger of the old Brembo calipers (uses 50 mm pads).
Honestly this is a very old set up, you may be able to find a used one somewhere, I used to have a Sodi Kart, shifter kart that had that exact system, and yes, you’re right it was also utilized on Trackmagic karts.
Here’s a link to that old caliper system. Hope that helps, I honestly would recommend just buying a new more modern caliper and bracket system.