That looks like the usual aluminum extrusion with endplates style of robust box. Unfortunately custom aluminum extrusions are
relatively affordable, even for limited volume production, and thus fairly common, so you'll have the devil's own time trying to find the original part if it was bought in as a box, or if it was custom for the OEM, an off-the-shelf equivalent.
If it isn't too long, it could be duplicated by machining from aluminum billet stock, but it certainly wont be cheap.
I suggest using an off-the-shelf box extrusion with custom oversize endplates, to provide the grooves that engage with the rods.