Basically what you are looking for is a generic bass case like this:

Amazon generic bass case: https://www.amazon.com/AW-Electric-Guitar-Carrying-Lockable/dp/B075MXG6YS

Sweetwater generic bass case (but the neck slot might be too narrow... may need to use a razor knife to widen it to fit a 6-string bass neck): https://www.sweetwater.com/store/detail/GCBass--gator-deluxe-abs-molded-case-electric-bass-guitar

Then there are cases that use this cube foam, and you cut a hole in the foam to fit your specific instrument: https://www.amazon.com/Guitar-Medium-yourself-Cutout-Guitars/dp/B00BUTGR2U