It’s kind of a specific item… Any shop that builds heat exchangers or a related item will have them.
Brass/copper/stainless tubing comes in them. They’re typically 1x4-8" boards, nailed together with 2x4s. Varying in length… usually 11’ or so.
If you work at a place that has any, or something similar let me know please and I’ll pick them up asap.