I made some from vinyl fence post materials cut with a chop saw to 4-5-5" and glued on a vinyl post cap (invert for use). I screwed a hole in the peak of the post cap to drain. I used industrial grade velcro to attach without drilling holes and you can stick them anywhere (inside or out) and if you change your mind just use some rubbing alcohol to remove the glue residue from the velcro. The white vinyl works fine with the Parker color. The materials are cheap and can be found at any home improvement store
I had them all season in by 2520 and they worked great. They never came loose and the size of the holder is good for cans, bottles, large cups (like ice coffee), and even for tools and other things when fishing. I found they were great to secure your fishing weights attached to your lines when you were moving to a new fishing spot.