Not for sale, but a recommendation.
Mine came from Rain and Sun (Southampton way?) Via the yard.
Expensive (£400 ish?, And doubtless more/slower now? ) Maybe that's why you're after a used cover?
VERY good quality.
I've just checked it over end of season, and renewed all the bungies (UV). Other than that it's pretty much as new, after 3 seasons of 6months use on a relatively exposed swing mooring.
I'll treat it with UV protectant this winter, while it's stored.
Essential on a swing mooring, imho. Keeps out rain, bird shite. Protects much wood, and allows mizzen to be stowed under (ridge pole style) so protecting that too.
I'd buy again.
One thing i find a bit odd, is the hole to allow the mainsheet to stay in place. I would normally remove my sheets, and secure the boom against "flopping" (and sheet from weather) with triangulated ropes to PnS aft cleats.