It occurs to me that you could try clothing-based signaling. On further reflection I remembered one period where I did pretty regularly have people approaching me, which involved a particularly nice winter jacket, and ended when I took the (faux, I think) fur-lined hood off of it.
For the opposite effect, I assume one would aim for 'frumpy', or at least 'generic'. My usual wardrobe is fairly boring; I actively avoid anything with a logo on it, and mostly wear plain single-color pants and shirts with uninteresting patterns (subtle all-over paisleys or florals, mostly; I'm not sure what the male equivalent would be). I also picked up a habit a few years ago of wearing a baseball cap whenever I'm out of the house; the incongruity (baseball caps are unusual for females to wear, and I make little to no effort to match my cap with my outfit) might be signaling something useful, but people were already approaching me infrequently enough before I picked the habit up that I can't really tell if it's made a difference.
I also seldom get bothered when I'm out and about. I wear single-color, logo-free shirts (though often bright red or green), with black or grey carhartt pants (which are pretty normal here), and a backpack. I often wear a jacket, even when it is warm, to hold my stuff and because I work in a climate-controlled room. Furthermore, I pay almost no attention to my head or facial hair. So about once a year, I shave off all my hair, and maybe thrice a year do I shave my beard. Needless to say, I exude "don't bother me!" when I'm walking or shopping.
Wha...
An exercise:
Name something that you do not do but should/wish you did/are told you ought, or that you do less than is normally recommended. (For instance, "exercise" or "eat vegetables".)
Make an exhaustive list of your sufficient conditions for avoiding this thing. (If you suspect that your list may be non-exhaustive, mention that in your comment.)
Precommit that: If someone comes up with a way to do the thing which doesn't have any of your listed problems, you will at least try it. It counts if you come up with this response yourself upon making your list.
(Based on: Is That Your True Rejection?)
Edit to add: Kindly stick to the spirit of the exercise; if you have no advice in line with the exercise, this is not the place to offer it. Do not drift into confrontational or abusive demands that people adjust their restrictions to suit your cached suggestion, and do not offer unsolicited other-optimizing.
To alleviate crowding, Armok_GoB has created a second thread for this challenge.