After spending way too much money trying to find a decent refill, I have FINALLY found one. This is the Schmidt EasyFlow 9000. It is inky and smooth and hasn't skipped on me yet.
To be clear- the Rifle Paper Co pen will take any G2/Parker Style refill. This is just one that I can really put my stamp of approval behind and am happy to offer in the shop.
It is a Medium point, so not as suited for super tiny handwriting styles. I'll continue to look for one, though!