Off road GPS bracket broke

I bought a TOM TOM gps for my motorbike. It is specifically made for motorbikes. I used it very seldom. The bracket that the GPS fits onto and that supplies the power to the gps broke. The gps could have fallen on the ground while Iowas driving was it not for the electrical connection. The gps was still under it's one year gaurentee when the mounting bracket broke. Now the company does not want. To replace the braketas they say that only thee gps is covered under the gaurentee and not the bracket. The fact is that the two of them is a unit as the gps cannot function without the bracket. It is a unit. They are dodging there responsibility. I am totally dissatisfied with their response that I should buy the bracket for R800.00.