Sure! If I can find it.

First thing I found was this: https://www.amazon.com/Koldot-Ukulele-Fretboard-Stickers-Chord-Fret-Beginner/dp/B088QWZ4R5/ref=sr_1_2?dchild=1&keywords=ukulele+accessories+finger+guide&sr=8-2

(By the way, Bernadette uses something like this for chords. For example, for the G chord, she'll put three red G stickers on the frets for that chord shape. And for F, she'll put two yellow F stickers on the frets. I guess they must be easily removable.)

This is not exactly what I'm talking about, but it'll work. The one my husband had was more like this -- a whole sheet you stuck on the fret board. https://www.amazon.co.jp/-/en/Melody-Ukulele-Learning-Stickers-Beginner/dp/B07H166H2C/ref=sr_1_5?crid=11JAJ3BDKAPH4&dchild=1&keywords=%E3%82%A6%E3%82%AF%E3%83%AC%E3%83%AC+%E3%82%B7%E3%83%BC%E3%83%AB&qid=1604748660&sprefix=%E3%82%A6%E3%82%AF%E3%83%AC%E3%83%AC%E3%82%B7%E3%83%BC%E3%83%AB%2Caps%2C312&sr=8-5

This one also has do-re-mi, and it's colorful for kids. His was the note names (A, A#/Bb, etc) only. His was also a cling, so it was put on and came off quite easily.