The Davis tel-tales are $8 for a pack of 7 (each color). They also have self-adhesive circles to stick them on. I bought a pack for a couple of sails I made for my dinghies.
A yard of the black 3/4 oz ripstop is $12. You could make a gazillion of them.
I'm not sure what Davis uses for their adhesive circles. This looks like it might work, for $12.45:
https://www.amazon.com/Mailing-Seals-Envelope-Sealer-Stickers/dp/B08XB4CY1H/ref=sr_1_3?dchild=1&keywords=adhesive+circles&qid=1629314645&sr=8-3Otherwise you could buy a yard of adhesive insignia fabric from Sailrite for $23:
https://www.sailrite.com/Insignia-Adhesive-Backed-White-54If West Coast sailing won't make them, and if there is a demand, you could start a cottage industry. $25 worth of stuff which you could sell for $8 for a pack of 7, after you cut out the gazillion of them.
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Bryan
Poplar Grove, IL
1977 Hobie 16 (died a spectacular death
https://youtu.be/Y7O22bp2MVA)
1978 Hobie 16