The above comments exactly. It's going to be a 14"x14" vent, and the hinge determines whether you're fixing a Jensen, Ventline or Elixr brand of vent.
This Camping World Link shows lots of them. I've sent a link like this before and shown only three, one from each brand. Now I see a vent brand called "Hengs" mentioned, and "metal" or "plastic" flanges. I hadn't heard of Hengs, and every crank-up vent I've worked on has had a metal flange.
I'm thinking you might be able to find somebody to climb up there an either 1. Carefully photo the hinge area with a smart phone or digital camera. Take photo and post here or compare yourself with the hinge areas in the CW webpage. or 2. Take a phone or tablet up there and compare looking at the vent with the examples on the CW page. Then you'll know what kind you need.
There's a wide range of prices. Part of it is how much the seller thinks they can get for a $15-20 item. BUT some of the covers are made of a much longer-lasting material than the cheapest ones.
To replace a Lid, typically you disconnect the link that raises the lid when you turn the handle inside. Then extend the Lid beyond what it usually lifts to. Bend over Backward basically. Then it'll unhook or slide to the side.
Suggest you replace them all if it has more than one. You can protect against future damage AND be able to open vents I the rain if you install covers. I think the part that's broken now is called "Lid" and now I'm talking
"Cover." There are many brands and colors. MaXXair is the common brand and they're good. Installation is four holes in the vertical part of the flange, no holes down into the vent base or roof.
