Appropriately sized piece of pool noodle?  Half a crab pot float?  I've picked up a couple, or several crab pot floats.  Haven't cut any up yet.  But figured about half of one would do the trick. Fast current might dictate coming back at somewhat slack tide..

heres mine

i got it at one of the tackle shops, i think the old light house, any that sell crab pots should have them. i put reflective tape on. i lost one one time after dark at the shoals. you might be able to 'pick one up'. look around ov beach or the hrbt island.

the clip is one of those metal stringer clips.  i try to keep the bouy close to the boat with alot of line out so it dosent effect the anchor set. and i face the blunt end into the current so its not easly buried by the current, keeping it way up on the rope helps to.

FYI,

Wilcox's in Newport News sells crab pot floats for $5.  They also have quite an assortment of fluorescent tapes (this stuff is expensive to say the least).

Chris