Reddit mentions of Higgins Waterproof Black India Ink 1 oz.

I like the idea, but make sure you know (a) how much ink cartridge refills cost, (b) whether you'll be willing to pay for them going forward, and (c) how easy they are to obtain. If they're only available online, you may want to buy a few packs with your purchase of the pen so you don't have to worry about additional shipping costs when purchasing later. (Don't go crazy and buy a lifetime supply, though - sometimes they go bad/dry out after a year or two.) My experience with nice stationery and art supplies is that if they're too expensive and/or difficult to obtain, you won't use them for fear of wasting them. So make sure this won't be a problem.

If you can't find a pen you like that meets these requirements, I'd suggest buying a nice writing journal and a pack of several decent-but-not-luxury pens to use in it. (Assuming you want to stay on the writing theme.) I have one of these MUJI pens and it writes quite well.

Another less expensive pen alternative, if you're more of the old-school fountain pen persuasion, would be a stick pen with interchangeable nibs and ink bottle. It's honestly not very practical but it's pretty fun to write with.

Daniel Smith Essentials set $23 , Arches Hot Press Watercolor Pad $11, Pentel Waterbruahes 3 pack - $13 , and a bottle of [India Ink $3] (https://www.amazon.com/gp/aw/d/B001E6CUPC/ref=mp_s_a_1_3?ie=UTF8&qid=1478233526&sr=8-3&pi=AC_SX280_SY350_QL65&keywords=india+ink&dpPl=1&dpID=51a6zmSbLPL&ref=plSrch). If I had a little extra, I'd spring for the da Vinci round 6 sable travel brush - favorite all around brush for smaller paintings :)

What about you? What would you have purchased? Or are you looking to buy?