One of the pop-up varieties a la Photoflex or Calumet would work, with room for getting 4x5 in/out of Grafmatics and into MOD54 adapter for Paterson daylight tank.

I'm tired of fighting my floppy changing bag.

I'm still in that "use the bathroom, but only at night when everyone's asleep" phase, so doing all this in a real DR isn't an option.