is there any chance that another car radio has the same plug that could be removed from it's cage and just stuck in the back of the riocar ?
please o please ?

Probably not but have you seen this thread?

I assume you want spares or something. If not why do you want to do this?

with spare plug(s), modified in-dash radio cages and power supplies you could have a 'jack' at every point you need.
I would be more that willing to pull a wire harness from a hole in my dash and plug it in the back of the headunit and then slide the whole thing into the dash.
I need this thing(riocar) in three cars, maybe four. and 4 channel out to the home amps would be nicer than 2
the horrible truth is that I'm having so much fun with this thing, that I've never even seen the cage for mine, much less it's plug. It could be missing for all I know.....it's still in the box. I can't bring myself to un-plug it from my computer at home.

So did you read the post I linked to? If not then read it. It's all about getting spare connectors (but not complete sleds) for home docking units etc.

I suggest you check for the sled though. You will need at least something like it for a car install if it's missing

yes I did (thank you, btw)
looks like a lot of users are in the same boat.
I wonder where else the plug is used (what other device) such that they could be stolen from dead what-evers.

I think you'll find it's on nothing that is easily obtainable. You're not going to be able to go down to the local junkyard and find it on some old beat up stereo.