When I first went vegetarian about 15 years ago and got asked why, my flippant answer was "for the chicks" (there is a long serious answer but the flippant answer wasn't completely untrue). I have wanted to turn that into a t-shirt for a long time and with the help of a graphic designer to make it look nice it is now for sale on Amazon.
You can now buy this on Amazon in a range of colours and in men's and women's cuts.
https://www.amazon.com/dp/B07B3NK89Z?ref_=pe_2196150_146773810&customId=B07537PB8M&th=1
This was done using the Amazon Merch service, where you can provide designs and they print and ship the t-shirts. The design was done with the help of a graphic designer who I found on https://www.fiverr.com. Once I have used Merch a bit more I will write a bit about it.
Unfortunately I think it only ships to the US so to get one anywhere else will require one of those postage redirection services.