This probably isnt what you're looking for, but you never specified a page size so...

I love thermal printers, like the ones that print receipts at the cashier. There's no ink; you just replace the little roll. They are great for text, just pipe a shopping list to lp and out it comes.

I have a printer for full-sized sheets but there's no comparison to the thermal on OP's criteria. Except open hardware... I don't think there are any printers today that provide schematics.