I don't know if this will help, but this was posted on a listserv I read:
In my lab, I used a custom made cable from a local company that made a male 50 pin amphenol to RJ45 connector for very much the same purpose you suggest.
There were 2 ways in which I used these
1) Aggregate multiple T1s onto a single amphenol wired back to a 110 patch panel.
Here I would use 6 of these cables on the back of a single system to aggregate 6
DS1s using a 258A. I would have the amphenol end plugged into each DS1 circuit
pack and then the RJ45 end would go to one of the ports on the 258A then use a
regular amphenol to amphenol cable to go back to the 110 wall field.
The benefit of this was that there is only 1 amphenol leading to the wall field to
support the 6 DS1s and on the wall field you only eat up 1 punch down block.
2) The same use you require where I would use 2 of these to connect systems back to back excluding the wall field and I would just use a simple RJ45F to RJ45F extension clip to link the to cables together. This works fine for short runs in the same room/building.
I can't recall the name of the place I bought from, but this place sells the same thing and they have it as a stock item.
This one is 25ft, but you might be able to get them to make custom lengths or maybe even a CLAN type adapter that provides just a RJ45 female connector.