looking for very very low profile vise or alternative

[magicniner]

I could, but don't they have tight tolerances and specifications?

Nothing that is impossible with good old manual bench-work, a sadly overlooked skill set in the "off the shelf" Maker Generation!

I wouldn't be able to achieve that for sure. thanks for the suggestions!

If you use lengths of 01 Tool Steel ground stock for the fixed jaw, moving jaw and the female threaded section for the screw you can make one with a bench, vice, hacksaw, scriber, centre punch, drills & a tap, some large threaded rod and some nuts.
Probably with the emphasis on the latter ;-)

- Nick