For smaller conventions, we have a semi-portable, a Model 14 tape printer in a road case made to fit. The tape is pasted down on telegram blanks, just like real telegrams up to the mid-1950s.
I normally run these off EeePC subnotebooks that run XUbuntu Linux. Those subnotebooks are about $30 on eBay, so I bought some of them for small projects. It's like having a Raspberry PI with a keyboard, screen, battery, and power supply all in a convenient clamshell case. I could run them as a Linux terminal, but I usually run them with a Python program that performs the telegraph office functions.
The lack of lower case is less of a problem in this application than the lack of emoji. I put the entire dictionary of emoji names into the program, and it spells out the emoji as (happy face), etc. That's amused some people who sent emoji-heavy messages.
The Right To Repair people would love those machines. Every part is individually replaceable. The price of this is a huge number of adjustments, plus annual oiling and cleaning. Few people today would put up with that much periodic maintenance in an office machine. It does let them be restored a century after they were built.