Both Comet and Diamond have produced N connector magnetic mounts. Pretty much any amateur antenna with 1.2GHz coverage and some with 900 MHz will be N connectors. Look for these models and others
Sounds like 2 right angle N connectors will do what you need. Connect them together and you should be able to get any angle you need.
But, like the others, I think there is some confusion. Do you have an antenna with an N connector on it, or is this a magnetic mount NMO base with an N connector on the end of the coax?
Following is a link to a page of N-to-N adapters (male to male, male to female, right angle, T, etc.). Maybe something there will meet your needs: N RF Adapters Product