You mean this one?
The black box and Euro style buss connectors (white thing) can be found at Sh_t Shack for a couple bucks. Glue the white thang into the black box with regular Crazy glue, it bonds the plastics together nicely. Then just drill the access holes in the ends to bring in the wires. Somebody did post a similar item now being made/sold by I think Blue Sea or another company a while back, but the only problem with it was it only had something like 6 terminals on it. With this, you can make it as big or small as you wish. I used the 3" by 6" box with two 12 terminal Euro thingy's, one of them I cut so it fit in the box, so I have a total of 19 connections. The picture below is an old one, mine's almost full now but you get the idea.