For what it's worth, you can get the cable itself very cheaply from various online stores, and the same places will sell you the requisite 50-pin IDC connectors. You can then make your own cables exactly to your own needs.
It's a piece of cake, and it takes minutes. If you don't have an IDC crimper, any old vise will do; if you don't have a vise you can get by with a plain wrench (just be careful about how much pressure you apply & where). There are gobs of youtube videos on making IDC cables, not that it's not self-evident how to do it.