pressure vacuum breaker at spikot..

I have a PVB atop a water spikot, then a line goes to a auto leveler for the pool.
I noticed theres a pretty good leak dripping down over the valve body from the top.
I am assuming theres a rubber gasket thats not sealing off and is shot, can this gasket be replaced or do I need to buy a whole new PVB.

I just noticed this and its dark already so cant tell to much more,,,
I did pull the plastic top cap off and its a Wilkins???

thanks
Chris

Check with the manufacturer for a rebuild kit...my understanding is many of them can be rebuilt.