Inflatable sanders are problematic, leakage being a problem with anything full of air. I decided to make a replacement from a piece of dowel, some velcro, and a bolt. The cost is less than $1. I really like the resulting round sander, and I hope you find it useful too.
Step 1: Dowel Prep
I cut the piece of dowel to ~2", diameter is ~1.5" this is a good starting size for my application. I then drilled a hole into the approximate center dowel, don't worry if you are slightly off, we fix that in post. Next I epoxy a 1/4" bolt into the hole; once the epoxy is set I cut off the bolt head.
Step 2: Centering the Dowel
Deburr the bolt if necessary. Next we have to center the dowel. This can be done by chucking the dowel into a lathe. Or chucking the dowel into a drill and spun against a sander. Both can be used to center the dowel, it is critical if the sander is to be operated at high speed that is be centered.
Step 3: Cutting the Velcro
The velcro has an adhesive backing. Cut velcro into a hour glass shape, you may have to try several times to get the right shape, stick it on to the dowel. Next cut a small circle with a wedge cut out.
Step 4: Template
Trace the template for ~1.5" or ~1" diameter dowel to a piece of velcro backed sand paper, then cut it out. Rescale the template may be needed if the dowel deviates greatly from 1 or 1.5".
Step 5: Using the Sander
At low speed (hand drill) the sander is ready to go when you stick the sand paper on. At high speed such as a die grinder, you'll need to use a rubber band to hold down the flips so that it does fall apart from use. Enjoy