All,
<www.lindgren-pitman.com> has a good selection of hard and soft buoys, including rigid long-line floats rated at 45# lift at 1000 feet (similar to the Nokalons we used in Europe but without the center hole, which is too bad, as that was a handy feature). We used them to add payload to the subs, for transponder floats, for released payload marker buoys, etc. They were handy as a pocket on a shirt. Everybody ought to have a few of these things.
L-P also offers the teardrop inflatables in various sizes that could serve as a releasable marker buoy for psusbs (the same ones that HBOI uses on the JSLs). They also have a dandy selection of plain old nifty bits and pieces. Highly recommended.