You can get a laser engraver or 3d printer for half the cost of those devices that's much more versatile.

These are based on the EBB board which uses a custom command set rather than the more common GCode command set which is the basis for most CNC machines.

If you're interested in CNC I'd recommend going with something that is based on GCode as it's much more transferable. GCode is used in everything from $100 PCB engravers up to multi-million dollar HAAS milling machines.

I appreciate the advice, but I doubt the laser engraver or 3D printer are going to hold a pen, so it wouldn’t really do what I wanted (of course they’re great to have in their own right).

There are countless examples on the internet of people adding laser engraver modules and pens to their 3d Printers. They're designed to be modified, they use an open source control language utilized by industry, unlike that pen device using a proprietary language.

The $150 laser engravers from Eleksmaker for example have an unused servo pinout on their control boards specifically for adding an accessory like an actuator for a pen. It would be trivially simple to swap out the laser module, which is held in by thumb screws, and replace it with a pen.