I've built one and own a second that I got as a Black Friday deal.
If you want a plug and play experience, just hit Fry's(or your equivalent) and grab what printer is in your price range. My son loves his XYZ DaVinci JR. (
https://www.amazon.com/XYZprinting-Vinc ... B00V3J8JEG)
(Link provided to describe it. You can find better prices that that.)
If you(or your son) want to learn more, pick up a kit for a Prusa i3(
https://en.wikipedia.org/wiki/Prusa_i3). I'm about to upgrade mine to the Mk3 variant.
They are not hard to build, and will give you a good understanding of how the whole process works. The kits are relatively cheap(
https://www.ebay.com/itm/Auto-Level-3D- ... SwCWFY8I1e). I built the original with my son, and he's now studying engineering in college. Coincidence? Probably, but it was still fun to learn
I would offer to print it for him, but my old one was knocked around in the move last year(hence the rebuild and upgrade), and I think that my son's is being used for a lot of engineering class projects. Feel free to PM me for my email address, and you can send me the file. If some time on the printer opens up(say, spring break or so...) I could try to print it. Won't make any promises, as a lot of files don't slice well(it's the process of converting a model file into the G-code needed to actually move the head and extrude plastic), and it sometimes takes a good amount of work to clean up a model for printing.
But I would never stand in the way of a young geek who likes both D&D and 3D printing! (Spoiler alert: I'm a middle aged geek who likes both D&D and 3D printing...)