

You will probably be best served with an industrial label printer, I used one while working in a grocery store to make tags. They come in toner varieties, so no thermal paper issues, and they are made to be portable. That being said, they are not at all cheap or simple. You are wanting to look into two companies, Zebra and Symbol, specifically at their mobile printers.
https://www.zebra.com/us/en/products/printers/mobile.html?page=1
To be fair, what you are asking for is nigh impossible without going thermal, and the reason can be summed up by one question: Where do you plan on putting the ink?
Which is very much OSRS. PvP is what single-handedly holds up the game economy there, while mega-rares and discontinued items prop it up in RS3.