xterraparts.com had the paint pens, they work pretty well. the problem is the paint will never be the exact match. i have alpine green, but every batch of alpine green that nissan made is gonna be ever so slightly differnt.

The clear coat also helps, the normal touch up paint isn't as shiny as the clear coat, so put the touch up on, then after that dries a couple coats of clear coat touch up makes it less noticeable.