Learn Spanish (Latin America): ¿Hay algún probador aquí?

Algún is the shortened form of alguno (meaning any or some). You must drop the final -o whenever the word comes directly before a masculine singular noun like probador.

The English translation says "fitting rooms" in the plural. Why does the Spanish sentence use the singular algún probador?

In English, we usually ask "Are there any fitting rooms?" using the plural. In Spanish, it is much more common and natural to use the singular for this type of question, literally asking "Is there any fitting room?".

Why is there an accent mark on algún but not on alguno?

When we drop the -o from alguno, the spoken stress stays on that final -u. Because Spanish words ending in -n naturally stress the second-to-last syllable, we must add a written accent mark to algún to force the stress to stay on the final syllable.

Could I ask ¿Hay algunos probadores aquí? instead?