Referring to the top part of a machine

I am writing some instructions in Greek that refer to a button that's at the top of a washing machine and I'm kind of stumped as to how to do it. By "top" I mean the top of the face of the machine.

Το κουμπί που είναι στο _____ της μηχανής...

It seems like their should be a word for it but I'm having trouble finding it!

Thank you!

If it's in the upper part of the machine face, you could say "στο πάνω μέρος της πρόσοψης". If it's on the top surface, you might say "στην πάνω πλευρά/όψη".

Also, you'd better say "στο πάνω μέρος της πρόσοψης της συσκευής" not "...της μηχανής".

το κουμπί που βρίσκεται... is a bit more formal than το κουμπί που είναι... It is a matter of taste, of course.