See current spec, prices and options here:
Gen 1 https://www.gtt.uk.com/product/mini-gen-1-gttporsche-front-brake-conversion/
Gen 2 https://www.gtt.uk.com/product/mini-gen-2-gtt-porsche-front-brake-conversion/
Replacement parts: https://www.gtt.uk.com/?s=porsche+replacement