We have a 2005, 19-foot Bambi; and the vent cover below is the one that fit our OEM vents. They only last about a year in Arizona, so I always carried a spare and changed them in the fall.
If you can get replacement lids made of polycarbonate, instead of polypropylene, they are worth the extra price. Polycarbonate isn't affected by UV, and they'll last much longer. The polypropylene covers crumble to pieces after about 12-18 months (at least, in Arizona).
I have since replaced both vents with FantasticFans, which have polycarbonate lids and last much longer (six years, so far, and they still look OK).
"New Style Jensen, without pins", available in white and smoke:
Jensen 14 X 14 Inch RV Smoke Vent lid J7291RSM-C New Style
Note: Link supplied for illustration purposes only. This part is widely available, possibly at better prices.