where can I get torque boxes?

US Car Tool has some nice ones, but they are pricey. They have some good shots of the boxes installed on cars. I have a set of their sub-frame connectors, nice quality.

https://store.uscartool.com/Torque-Boxes-Set-of-four-4-for-1967--1975-Mopar-A-Bodies_p_34.html