[McGillicuddy]

Don't know what you have but conceptually it sounds like some kind of single pole friction catch seachoice makes some too
here are some:

http://www.westmarine.com/1/1/5655-i...om-seadog.html

http://www.technologylk.com/_R7079/c...m?src=shopping

http://www.amazon.com/gp/product/ima...70768&sr=1-210

I've also seen some nylon ones where the screw goes in a cylinder, like, well, you know...