Did you know that Rifle Paper Co pens are refillable? We've tested lots of UK refills, and although there aren't a huge range of compatible refills (and no traditional rollerballs that we've found), we have found a couple which fit!
Ball point refills: Parker Quink Flow Ballpoint Refills
Gel ink refills (more like rollerball ink): Parker Quink Gell Ball Refills
You can see our full range of Rifle Paper Co pens here.