Hey Joe. I have been on this same quest for a few years now, for similar reasons. These are some things I have found out in my search:
• Gibson SG short-scale basses are really freaking light. They're not for everybody, but the ones I've tried are super lightweight.
There are many versions. Here are a few:
Gibson.com: SG Special Bass
Gibson.com: SG Standard Bass 2015
• A Kiesel Vader could be something to consider. They are headless, which already removes weight. You can spec the lightest species of woods, and get it chambered to reduce the weight further. You can also pay an upcharge and they will find the lightest pieces of that species that they have in stock for you. They did this for a headless 8-string guitar I ordered, and it's light as a feather.
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• The ibanez mikros might not be of the level of professionalism you're looking for, and they're micro scale, but they are really great basses and ridiculously light.
4 string:
Ibanez GSRM20BWNF miKro - Walnut Flat
5 string:
Ibanez GSRM25BK miKro - Black
Good luck in your quest!