Just an update on this. I don't necessarily want to gig with my 60s Fender case (maybe a thief magnet, and I don't 100% trust the handle!) and the aforementioned Fender Short Scale gig bag is very light and offers little protection for anything more than carrying around on one's back.
I went to Gear4Music in York to try a case which on paper fits the mustang quite well - my bass is about 42" from strap button to headstock (I think the reissues may be a tiny bit longer due to more body behind the bridge) but I'm happy to report that the Gator Icon guitar case fits perfectly. There's a removable cushion at the bottom which would offer extra room if you needed it.
I'll post a proper pic later but it's a great case, comfortable handles and straps, lots of pockets, rain cover, semi rigid, light weight...
https://www.gear4music.com/Guitar-and-Bass/Gator-ICON-Series-Bag-For-Electric-Guitars-Black/5DL2