Actually, I had a couple of Bally's a long time ago (A 5500 and a 6000), but I really don't remember what the fuses holders looked like.
I hated them things... pushing that stupid little button on the front forever to clear stuff when there really, there should of been a switch!
I think my thumbs are still indented.... lol
In your photo, the fuse inner body actually looks like the fuse holder from an S+ power box.
Those are fairly common.
If I were you, I'd give Jim of Midwest Slots a buzz.
His phone's number's on the NLG Homepage up top where the vendor's are listed.
I'll betcha he has one.
I dug around but don't have one....they're all in the power supply boxes.
If Jim don't have one, place a WTB ad in the Classifieds section of NLG and hopefully a vendor/member will spot it and have one for you.