You can cut a piece of hardboard that lays in the ashtray recess perfectly. You just round off the corners. Coat of black and it looks part of the furniture. Into this you could put sockets I guess and add some clips so it can be levered out if required.
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I gave my ashtray to a guy who said he planed to do this,i have no need for an ashtray as the dash tidy covers the hole. Whats an I pod? I have a mini disk. Couldlt you use some of that kids play mat foam or a swiming float and cut it out for a nice insert. Or use the display insert you get in the box for a mobile if you get one with an i pod and use it for a fibre glass mold if your feeling clever. Bet a decent mold made one up for grabs would sell too.