Never seen anything like that, but let me tell you what I did.
My JVC head unit has a aux 1/8" connector on front and a changer control on the back. There is an adapter you can get that turns the changer connector into a standard Dual RCA input.
I suppose you could use the aux connector for 1 input and the changer for the other, which might do what you want.
I can't remember why, but the changer adapter would not work with my head unit, so I ended up tearing it apart and soldering the front aux connector to a 1/2" female adpater, which hangs out the back of my head unit.
Anyway, it's a long shot, but something to look for. My HU isn't made anymore, but I think any of them that can control a changer and have an AUX in would do it.