I need large OD empty spools

I want to standardize my in-house filament management needs by respooling all my filaments onto one size. Preferably that size would be large OD with large hub OD and narrow width, perhaps something like 8x4x2".
This would also remove the excessive curl caused by small hubs, especially since I use 3mm.
I have looked all morning for spool stock but is surprisingly sparse options. Plus new spools can be $5 or more; ridiculous considering how many users must have empty spools laying around.
I would like about a dozen and I am in the US, if you have some or know where I can look. Chinese distributors usually require large minimum orders and for other reasons is my last resort.
thanks for your help.

Sounds like a perfect job for a 3d printer

Here is what I'm adopting for filament storage and feed supply for the printer I'm building.

I thought about printing but that is overkill considering the should-be-dirt-cheap injection-molded parts that must be flooding the world (I also don't have a big enough printer right now).

You can make a spool out of any two discs and a smaller cylinder. Maybe you print the cylinder and screw on the discs.

Better yet, copy what Reelex does and keep the filament without spools.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]