Hey RTodd:
You might want to check this bag out.
Seriously though, you might want to give timlittle a call or PM. He works for Carter bags and sells used bags and SMBs for pretty cheap; he might have something you're looking for.
Also, I have a Carter 35 pound Personal Float, 60 inches tall and 5 inches wide, and it has a volume of 0.5 ft3. It doesn't take much to inflate at depth but I don't know if it would be exactly what you're looking for. If you want, I could send it to you to try out and see for yourself.
I hope this helps and good luck.
With kind regards,
Thomas
Thanks for the info. I have the Carter 50 but it doesn't stand up well. Is the 35 easy to get to stand up straight? I don't want to have to "hang" from the float to keep it upright. The site says a 4 lb weight will make all of them stand up. That just isn't true with the 50.