There was a thread earlier about people wanting to show support but that the t-shirt designs from the EU parliament store aren’t subtle enough
The channel Eurosport also has some items on Vinted. Their designs are tasteful in the sense that it’s e.g. blue stars on a dark blue background
You can actually download the Conformite Europeenne .svg file from wikimedia and upload that to a local “design a t-shirt with your embroidery” company