I have spent the better part of the day playing with ink refill options. (I write with my left hand, and understand that some are better than others for lefties.) I actually turn what I am writing on sideways.
I have found a nice gel refill made by Parker. Just screw the tip off the M.A.P. pen, drop it in - done. I will admit, I do like the gel very much! The Parker GEL .7 #30525PP, is available at most office stores. So if you prefer gel ink, this particular one works with the Burke M.A.P.