How will you secure it without bolt housing in the frame?

I’ll sit it higher so I can strap the top half of the box to the seat post (velcro strap) and it won’t fall down as it is above the top tube and bottom part around the seat stay. I’ll velcro it to the seat stay (vertical). Design will be so it wraps slightly around seat stay so there is still some form of aero shape.

I'd just throw a quick tack weld on it and call it a day...

If you are printing your own, why bother getting the specs of their box, customize it to what you want!

Exactly what I was going to respond when I read the first post.
If you want the manufacturers version. I'd just buy it. I doubt you'll print something better or cheaper.
If you want to modify it for different mounting but still keep the original shape, it might well still makes sense to buy one and modify it.
If you're printing it, and you already have a different position in mind, I see zero reason to look at the existing design.

For one thing, the seat post is narrower than the seat tube, so perhaps you'd change the profile slightly.
Secondly, if you're mounting it closer to the saddle, and especially if you have any sort of behind the saddle water bottles or repair kits, you may find the lid doesn't open without hitting off something.

If I was making my own, I'd make my own.

I need a draft box if anyone has one

I have a design that you can start with if you want.

My plan was to put one hole in the frame to mount the bottom. The stays on the IA are so low that you'd need to build a MONSTER sized box for most sizes to get it secured down there. I wouldn't recommend that. Mine secures to the seat post with a bolt through the mounting slot. PM and I'll get you some solidworks files.