My Dad would sometimes address us as “Dudes and Dudettes”. He would also call us “Sports Fans”. Dad was, in his own way, Peak Boomer.
It think Dudette is about the best as can be expected. Dudess doesn’t have the same ring and Dudie would be a mistake.
Or La Duderina, if you’re not into the whole brevity thing.
or, if you are using the Xerox machine, It’s the Dudemeister / Dudemistress
I’m thinking a Dudemistress probably wears tall boots with spike heels. Probably not the best term for random women, and especially not random children of the female variety. 
I’m over 70, and, yes, in Southern California, and I use dude all the time. Not linked to gender.
You’re just young at heart
I heard a snippet on npr some years ago (maybe 15) that some urban youth (Philly area IIRC) had taken to using a gender-neutral third-person pronoun which seemed to have arisen somewhat organically. The word was “yo” – obviously it did not spread.
Ha. Nicest thing said about me in ages. 
I like David Lynch’s take:
This whole world is wild at heart and weird on top.
No idea what it means, but I like it.
Dudarino? Dudster?
Lynch made a movie called Wild at Heart in the early '90s. It was, IMO, possibly his best piece.
I agree with you. It’s the only Lynch movie I really like. His others are always try-too-hard for me.
Gaylord, immediately springs to mind
Georg would be a good one. “My name is Georg Naseyzhen”.
They’d probably tell me I’m at the wrong BK, Gaylord is 150 miles away.
I live in Switzerland. Many people who are above 50 like to bemoan the fact that most under 30s use only “du”. I’m not Swiss, so I think the whole language switching due to formality is tedious. But I follow the rules.
After 20 years of getting my hair cut at the same salon, I am now at “du” form with the woman who cuts my hair. Mostly because I screwed up and called her by her first name, and we discussed it and decided to go to a first name basis. She’s 2-3 years older than me.
It was quite common in my highschool, but most of the time we were “dudes” whether female or male.
For me, too.