Couldn't you just use 4 Y connectors to achieve the same ?

If you are only having the scanner OR the amateur radio on at any one time it would work OK.

So split each mono signal into two with the first two Y connectors, and then feed one from each into the Y connector the the left AUX and the same for the right AUX. OK so it's the not the greatest for sound quality but it will work.

You would not be able to name individually however ... and I'll leave the combinations of connectors up to you as I don't know the connections on the scanner / am. radio ... possibly mini jack ?