I'm more of a 46-30 specialist. Dolan had them both on their website and on Ebay, but that combo is sold out apparently. Alex's Cycle in Japan should have it though, and they ship to the UK.
Also, do you really need a 172.5? #internetbikefit
You might be better off buying a 44-30 from Dolan and changing the outer ring then. The FSA ones are basically OEM only, and I don't think you'll convert a 7803 or 6603.
I'm more of a 46-30 specialist. Dolan had them both on their website and on Ebay, but that combo is sold out apparently. Alex's Cycle in Japan should have it though, and they ship to the UK.
Also, do you really need a 172.5? #internetbikefit