I am looking at a unit missing these.

Is that for the VSS and backup camera only?

I know some say you need VSS for navi to work properly.

Are these pieces readily available?

VSS affects navi tracking accuracy.

Reverse signal lead is for backup camera and also for tracking accuracy (i.e. prevents the map from rotating completely around when going in reverse).

 

My memory is hazy, but I thought those extension leads just had bullet connectors on one end and wire taps on the other. Crimp-on bullet connectors are fairly easy to find and so are wire taps. You can make your own easily and for a lot cheaper than Pioneer would charge for them.