I have a a client who is in love with felt pens. He uses the everyday PaperMates typically, but has a momentous birthday just ahead and I'd like to help him up his game.

So, the question is: which major high quality pen manufacturers have a built-in "felt option" available, or have felt tip refills available to convert a rollerball or ballpoint pen into a "fancy" felt tip? And, if there are several options, I'd love the experts here to guide me a bit on highest quality available as well.

I'm a FP guy through and through, but can't help but up the game of someone I respect...if even just the pen body

THANK YOU in advance. - Rick