Flourescents glow under blacklight, as does anything with optical brightener. Wilflex used to sell a clear called Luna Clear that was just soft hand with OB in it. No real sales, so it is a non-standard now.
BTW - yoga mats are plastisol. Yup just a foam plastisol that is metered onto a belt. I used to sell industrial plastisols into this market before it all went off shore to China. You can print standard plastisols on them with pretty good results as long as the temp stays below 330 or so.
