I use this for all the paint inspection marks and lettering, they offer tons of colors.

https://www.ebay.com/itm/1-4-Pint-1-Shot-103L-POLAR-WHITE-Paint-Lettering-Enamel-Pinstriping-One-Shot/383592333752?epid=1542383945&hash=item594fe281b8:g:FLYAAOSw4nNgKj5m