Away from the house, will try to remember to try to find it. Might have been this: https://www.amazon.com/Hiipoo-Waterslide-Transfer-Transparent-Waterproof/dp/B092V22XWZ/ref=mp_s_a_1_13?keywords=waterslide+paper&qid=1677886059&sr=8-13

Or maybe something different. Definitely not marketed as being for models. Turns out it didn’t matter. Maybe I just got lucky.