52/36 Chainrings for Ultegra 6750 crankset I have standard compact (50/34) crankset. It seems to be to small for finish on flat stages. I am going to replace chainrings for semi-compact.
I've found that absoluteBlack offers products for older crankset like mine
Premium Oval 110 4bolts 


Do you know if there are any other chainrings (52/36) for 110BCD 5 bolt which fits Ultegra 6750 ?
Yes, there are. Any 110BCD 5 bolt chainring except Campagnolo will fit. If you want to keep the smooth appearance with hidden chainring bolts, at least Specialites TA and Stronglight make compatible chainrings at wide range of sizes.