Found these today at an Arts & Crafts store, each $2.99. Various colors.

So far, I've painted an orange stripe on my Fenix, my Griptilian, and an OD plastic container on my daypack. Dries quick, not Blaze Orange, but a good contrast. Easily bright enough to see if you drop something around a campsite.

http://art-supplies.misterart.com/store/view/001/group_id/1320/Sharpie-Paint-Markers.htm

Various dealers on-line have differing prices.