have you looked at the NRJ4HM-1, it looks to me that its a tad smaller, than the NRJ6HM-1
OFF TOPIC (RANT): now that i really think about it, cant you just have a hole where a 3 conductor cable leaves the enclosure through the top and on the end are 2 female jack connectors, this gives you the flexibility of the small enclosure, but without the hassle of bulky internal connectors. also, the biggest problem i have with 1590A is that the width of 2 L shaped jacks is more than the room you save on the board, if i want compact, ill top-mount the jacks. (not that i want to discredit the skill and precision involved in building something in a 1590A)
cheers, Iain