I bought this one this week. Dimension seems too small but it’s a perfect fit and good value for money.
https://www.musicstore.com/nl_NL/EUR/MUSIC-STORE-Keyboard-Bag-KCS-III-98-x-25-x-10cm-20mm/art-KEY0004919-000
This a very good question. I am also looking to an answer to it. I want to use registrations in live gigs, where I use ForScore on the iPad to send midi commands upon song selection.