My local bike mechanic tells me that I have worn out the teeth on the larger chain-ring of my 2016 Cannondale Synapse road bike, and that I need to get a new one; he says he can't get one through his normal channels and that I should look online for one.
Well, I looked online, and they do seem to be difficult to obtain and rather pricey as well ($180-$300), which makes me wonder: do I really need to get that exact chain ring, or are there other chain rings of the same size (50/34T) that would be cheaper and work just as well? How strict are the compatibility rules for two-gear road-bike chain rings?
FWIW the bike has the Ultegra groupset and Di2 electronic shifting, with 2 rings on the front and 11 gears on the rear cassette. Cannondale's product page for my current chainring part is here.