The general consensus I've read is that gig bags are evil...
Having said that, I use a gig bag almost exclusively. Granted, I'm not playing clubs very often at all - mostly very controlled environments. If I do play a less controlled gig (outdoor festival), the bass goes in a road case.
The only place I found a bag that would properly fit is from Alembic. Unfortunately, it looks like they've stopped stocking/offering them. They were pricey, but very well made - and they FIT.
There are bags out there that would appear to have the width to hold a large standard Alembic, but it's the length that gets ya. The longest internal dimension I've seen quoted is 50. My basses measure out to 51 & 52. If you have an older Omega, it might be just at or under 50. I remember hearing that JimmyJ used to use a Reunion Blues bag. I talked to them years ago and know that the original bag pattern was for a 50 internal length. And we all know that Jimmy plays an older Omega.... ;-)
Good luck with the hunt. Let us know what you find.