A remix of brycelowe's design. I added a hole that's large enough to accept a BIC cartridge and adjusted the size. It's a bit top-heavy, but it looks pretty neat.
To print it on my X1, I had to split it into four parts and then fuse them with a lighter, but that's just because it had a weird layer shift issue and I couldn't be bothered to fix it. There's no reason that the model shouldn't work if printed upright.