Bersa Thunder 380 maybe, or a Walther PK380? if I had an FJR handy, I could test with mine. NOT 9mm in the usual sense 9380 ACP rounds are 9x17 v. the standard 9x19 for a "Luger" or "Parabellum" - which is what we all think when we say "9mm".
Echoing the issues around concealment form the public - less so about security. I'm willing to trust you're not a total bonehead and understand that the dash is not a "secure" space per se, and that YOU will take it upon yourself to properly secure any firearm.
Some folks mentioned options...
Carrying while riding? Maybe, but tougher to get to under layers of ATGATT and wouldn't it just suck if your concealed holster accidntly coughed up your sidearm along the road without you realizing it? Nevermind how it would feel if you happened to go down an dland on the gun...oooh...that'd suck.
Under the seat makes sense if you feel you won't need to access the gun - I mean, you'll use it when hiking around camp at the end of the day, but while traveling, you feel you won't need it.
Saddle bags - make more sense as "secure" storage, but could be argued are easier to steal, too - and accessing the gun is almost as restrictive as under the seat.
...and while the bra might not have worked for that unfortunate lady who shot herself, perhaps it's the best bet for the OP after all?