What is the name of the place you put sheet music on a keyboard?
I have a yamaha keyboard and I can’t find the piece that you attached to it to put the sheet music on. I want to try to buy a replacement, but I don’t know what it is called, so I don’t know what to google for.
Have you tried looking your keyboard up on Yamaha’s site and seeing if they sell accessories? Otherwise, I’d be very surprised if Yamaha didn’t have a phone number for you to call for exactly this sort of question.
Or talk with your friendly neighborhood Yamaha dealer.
But if it was like the piece of crap on my DX7, you’d probably be better of buying a regular music stand and using that. . . .
You can have the one that came on mine (PSR 275) if you come pick it up. 
Barring that, you can call 1-800-79-YAMAHA. If you give them your keyboard model number and tell them you need the music stand, I’m sure they can help you out.
Music rack, to answer the question.
And Miss Purl McKnittington is right. I’d look on Yamaha’s website.