Have you ever put it in a ziplock bag and squeezed the air out?
Maybe it will take less room.
When I go on overnight trips, I pack old underwear and socks vacuum sealed in bags, then throw them away.
I've fit a weeks worth of clothes in a standard tailbag and small tank bag.
2007 Honda 919.
Used to be Red, now it's Green. Open for name suggestions.
If you really want permanent onboard storage, change out your exhaust to the 2 bros single side exhaust and get the matching storage canister. This makes it look like you have 2 exhaust outlets (like stock), but you use one side for storage. Comes with a locking cap and all that good stuff.
A small leather bag that would attached between your forks just under the headlight sounds like it might fit the need for jacket liner storage. Might not be too noticable. My dad has one on his '03 1100 Sabre. Not sure how one would look on a 9'er though...just a thought.