Re: Boat cover - for in water docking, not on a trailer
All the mooring covers on-line will show straps, but these are used for towing only -- this makes the mooring cover 'trailerable'. If the cover has elastic around the edge, it's a mooring cover and you can use it while the boat is docked or just sitting on a trailer and not being moved. Just about all will come with straps or offer them as an add-on (and they are always pictured!). The straps are not permanently attached; you use them by looping them on. Most come with clips to connect to themselves.
Your size boat has plenty of options for what I described: Basic cover with elastic. If there are straps in the pic, that doesn't mean it isn't a mooring cover.
In a few mins, I will post links.