Migrated to:
https://www.printables.com/model/541805-rockband-drum-kit-replacement-battery-door
Title says it all: Daughter broke the tab on the battery door, and rather than try and glue it, I made a new one. Plenty of trial and error...
Technical
I used PETG at 90% infill. Careful with the support - gonna have to trim it out carefully if your settings aren't awesome.
You may (will?) need to trim the little lips that go under the locking part of the drum kit to get the fit just right, and the door to stay closed. I used an Xacto knife.