Uniball vision rollerball pens basically glide on the page, and they're portable unlike fountain pens. They're also significantly cheaper than buying a fountain pen + ink(s). As much as I love writing with my Sailor ProGear Slim F/EF nib fountain pens, inks + traveling = a nice mess waiting to happen.

I had a pelikan souveran r800 that was refillable, but sadly I lost it on one of my return trips. Now I just travel with 3 leuchtturm notebooks (A6-grid, A5-grid, B5-lines-softcover) and a bunch of uniball pens.