I think all of the old 6GHz 8753ES VNAs at work had APC7 connectors and the company permanently fitted (APC7 to SMA) or (APC7 to N) adaptors on them. These adaptors were from Suhner and were quite expensive. However, the VNAs were still used up to 6GHz with good results using either an 85033E or 85032F cal kit.
The home/hobby alternative would be to buy used APC7 to SMA adaptors from ebay (maybe $60ea) and make a homebrew SMA cal kit for less than $30 using decent SMA connectors from Suhner or Johnson.
It's also possible to make a homebrew N cal kit to suit APC7 to N adaptors but this probably won't be as easy to correct as a homebrew SMA cal kit. A homebrew SMA cal kit can give good results up to a few GHz if constructed carefully.