The small thermal printer takes 53 mm width or smaller, so “A9 size, 37 x 52 mm, 1.5 x 2 in”.
The big thermal printer takes Legal (216 x 356 mm) or smaller.
For context, A4 size is 210 x 297 mm, 8.3 x 11.7 in. (Width is the only important part tho, tbf.)

https://doubledragon.co.uk/shop/printers-labels/adhesive-thermal-labels/57-30mm-sticker-thermal-paper/

https://paper-size.com/c/a-paper-sizes.html

…. Ok now what would be great is https://www.globepackaging.co.uk/6-x-rolls-of-extra-strong-reinforced-gummed-paper-water-activated-tape-48mm-x-100m.html if the roll itself were smaller so I could print on that — wait, probably doesn’t have the whatever that thermal paper has. :/

Ok so the Pocketjet PJ-663 manual says,
“- Avoid contact with Diazo (blueprint), carbon-less, or cast-coated papers.

- Avoid contact with vinyl or acetate materials, such as many notebook or report covers.

- Avoid contact with organic solvents, oils, and ammonia.

- When using a coloured marker, be sure to use one with a water-based ink. If you use a solvent-based marker, it may darken the paper.”

So like, I can watercolour just fine, but not acrylic paint them (fine by me).
The laminate is made of PET, which is polyester?
Is polyester “cast-coated”?

NERDS!
Can I use laminating film in a thermal printer to laminate thermal paper?

I don’t have either yet, but I bought a got thermal printer for printing my course forms without further HP-inflicted mental rate abscesses.
I was looking at paper so I’d be ready to print my coursework for next class and the ebay ads confused me for a second.

… also I want to print stickers. For morale!