A Cloth Merchant
Markings disappear with heat. The cap has a rubby thing you can use to erase the mark, but an iron works better on fabric.
Test marker on scrap fabric to make sure it will disappear.
2-Hole Horn Toggle
32mm Concave Horn Button - Brown / Black
50 Fabric Animals - Marie Claire
A Textile Traveler's Guide to Guatemala - Deborah Chandler