Yes I looked at this...here in the UK (when I looked about 6mo ago) it was actually cheaper to buy a cheap 4" or 6" caliper as a replacement head (about £7) than the replacement head itself. It seems the expensive bit tho is the stainless steel channel and the PCB. I'm wondering if these PCBs are machined rather than etched? It might be possible to make a new PCB/channel on a CNC machine and get the accuracy needed - it would be interesting to try. I've not found anyone selling the channel seperately, maybe because they are pretty indestructable.