While I'm not familiar with Cal-rods, I have an old Tex-air dryer from the 1970's and I get the finned heating elements custom made by Vulcan Electric (https://www.vulcanelectric.com). They also have "component tubular heaters" (https://www.vulcanelectric.com/products/component-tubular/) which may be what you're looking for. I initially called them and spoke with the engineer who spec'd out what I needed and now I just reorder when needed. Might be worth a try. Good luck