Hey, cheer up

Public misgendering even happens to cisfolk occasionally.
Unfortunately you're kinda seeing what it means to "pass" or "not pass". Even though your identity is valid no matter what, society is still set up largely on a binary scale. Everyone wants to say he or she, because that's what it's always been. At a glance, you probably just look like a very tomboyish woman.
You'll find that people will be determined to gender you, actually. They might search for nametags or ask for you name, and try to make a guess. Names like Jordan and Ryan would stump me. They might listen for someone use to use a he or she first. Somehow, they crack it.
This is sort of why going full-time is a major thing. You have to really change a lot of details if you want to be properly gendered. Unfortunately for me, I'm even asked if I'm just a gay guy sometimes... It's a bit of an adventure.
Many *hugs*
I'd experiment around some more in private and see what you can come up with. Generally, most people are going to have to decide if you are male or female. Most people don't use the "they" pronouns. Also if customers are regulars, they may set their decision in stone to use on mamy visits to come.
Also, cut your coworkers some slack. I'm sure you already have, you sound too innocent to be mad at them. Habit is something hard to break. Same thing for regular customers if they're ever in the know about this.
If you aren't happy with he or she, unfortunately you might want to settle for one at some point. I'm more okay with she than he personally. Even though my gender identity is fairly empty, I'm more than okay with expressing myself as female to get those she's instead of he's. Given, I'm not the girliest girl, because that's just not me. In a situation where you feel totally gender nonconforming, you miht learn to not care. For some folk I know it actually made them feel better to get half and half. And every once in a while, if you make it truly hard to tell... You do find that some people eventually give up, and avoid pronouns altogether
Just some scatterer thoughts, dont know if it's much help. But hey, cheer up

It gets better.