The Off White Ceiling Garnish # FVK1060-80 will fit your application perfectly. It has the 6" leg that you'll need to cut down to fit your 5-1/4" application but aside from that everything else will match up perfectly.
If you need a White garnish instead you'll need part # FVK1060-81.
Attached is a review video of the white version for you to check out. view full answer...
Unfortunately we do not carry the motor for the Northern Breeze model so I recommend replacing it with the Ventline Ventadome Trailer Roof Vent w/ 12V Fan # V2094SP-34. This roof vent uses a 12-volt fan to circulate air in motor homes and enclosed trailers, keeping interiors ventilated without compromising security. view full answer...