The clamshell cover that Wes showed above is exactly what installed over all four of my vents on my Pilot 34. I agree, it is impossible for normal humans to reach inside to get to the hose and replace that vent fitting.
Those fittings are plastic and the sunlight destroys them after a dozen years. So I just put angled clamshell covers over them and all is good.
This is what I used: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I had to trim the locking ring of the crapped out vent fitting on the sides with a chisel to fit nicely under the small clamshell cover. On one of my vents, I had to trim back the length of the fitting. This was the holding tank vent and I suspect that it was bigger than the others.
But it now looks like Mainship built it this way.