Roll paper cutters are exceedingly scarce these days. And if you do find one it'll most likely be as large as a casket, weigh approx. 150 lbs. designed to handle up to 52" rolls and to be wall-mounted.
I use both a Meteor Seigen and a Kreonite. I have them on castors so I can roll them around. Both these models were available in shorter versions but I've never seen them in the compact sizes. They seem to be much more common in the EU than in the states.
A word of caution in the chance event you locate a cutter and choose to have it shipped... These things are basically a sheet-metal clam-shell box containing a heavy rubber-coated roller, a motor, a rotary cutter and an anvil. The cutter and the anvil can be twisted out of alignment fairly easily if the cutter has been stood on its end. Also, keep in mind that in the event you do find a roll paper cutter, chances are it's over thirty years old. I mention this because many were fully automated and the programming controls get sticky and unreliable and the capacitors dry up (especially when they've been sitting in storage). For this reason I think it critical to fully test out a unit with a roll of paper before purchasing.
Another consideration is to cut your paper using a roll-paper compatible inkjet printer.
Good luck finding your cutter!