$50 each. I have two. I purchased these hoping my girlfriend would be more willing to get out on the water but unfortunately that didn't work out. They've never been used, only tried on.

Minimalist Manual Inflatable Belt Pack from Mustang Survival. Model: MD3070.

A discrete inflatable belt pack for inshore paddles that provides up to 16.9 lbs (75N) of buoyancy in a pillow-style bladder when inflated. Perfect for reservoir paddling.