1996 Lance 3000 Main Roof Vent Operator Replacement?

Hi guys, I have a bad main roof vent operator and I am full time on the Oregon coast. I have now had to climb up on the roof one too many times and need to replace the operator. The small wheel at the and of the bar has either worn down or fallen off but the apparatus pulls out of the slot and the wind whips the vent cover back in a hurry. If it rips off, I'll be quite screwed!
My question is are there different sizes of these operators and how to approach purchasing. I found this one on Ebay and just not sure if it's a fit.
Any assistance greatly appreciated up front.