There are direct replacements you can get if you let me know the size, make and model of your current roof vent; otherwise, you can just use a universal replacement cover which will work with any roof vent on the market.
For a universal roof vent we have the MaxxAir UniMaxx Universal Replacement Lid for RV and Trailer Roof Vent # MA00-335001 for translucent white or # MA00-335002 for black. view full answer...