I actually have a waaaay harder time dealing with customers than coworkers.
I do have a hard time talking or befriending coworkers, but I can get a long with them, while when I get customer support calls to direct I just panic and shake. At least I'm acquainted to coworkers, but I know what you mean, I still really want a job with minimal social interaction, but alas, my experience and lack of college education limits me.
But let me think, I think jobs at smaller companies you'll have less coworkers to deal with. I work at a small(ish) software company, it isn't big or crowded and there are not cubicles, I work at the front desk and it's freaking quiet out here and I only have brief interactions for the most part.
I've heard that warehouse jobs are pretty good for introverted people, but I dunno about anxiety or coworkers. I think working at a warehouse would be rad. Other jobs off the top of my head that seem like they're minimal with coworkers are: Graphic Design, Data Entry, Lab Assistant, Land Surveying, IT, maybe something janitorial?
I can't think of anything else, with self-employment you'd have zero coworkers of course, but that's a little tricky to pull off.
It seems like different jobs have different sorts of coworkers, I always hear horror stories about really terrible coworkers, but everyone I work with has been pretty nice, and most people seem to keep to themselves. Maybe if the opportunity arises quit your current job and try a different place, the people that work there could be completely different and less like they're high school kids.
I hope I could help a little!