Guessing from your handle that we are talking about a 71 the only thing I have seen from a parts house related to the tool boxes for these models was the fiberglass box itself.
If my assumption of your truck model is correct I would suggest you contact all the various suppliers such as American Classic, Jim Carter, Year One, LMC, NPD, etc and ask them. Your only other option, other than salvage yard or ebay trolling, is to post a "Wanted" ad in the Swap meet section here or on another website focused specficially on the 67-72 series. There are several.
Good luck.
