Not an exact answer, but instead of the round dust masks, I have ear-loop face masks. They store flat, and maybe cost $10-$15 for a pack of 50 at your local medical supply store.

I also keep an extra large red bandana with them as backup.

What about those new 1 1/2 cup Ziplock bowls? They seem about the right size and they are round.

Or maybe you could use a tupperware container just big enough to store your goggles as well as the dust masks, and ball up a bandanna behind them to keep shape. Keep a pair of ear plugs in there as well?

Just some random thoughts.