I tried
Piano music desk pins
Music desk clips
I found https://www.amazon.co.uk/The-Piano-Accessory-Shop-Bookholders/dp/B01JGRD0JK/ref=asc_df_B01JGRD0JK/?tag=googshopuk-21&linkCode=df0&hvadid=310886154238&hvpos=&hvnetw=g&hvrand=3492565074610097967&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006523&hvtargid=pla-697661771209&psc=1
Is this what you want?
Iain