Foam gaskets for double sockets on uneven walls

[SpannerSpark]

Does anyone know where I can get foam gaskets for double sockets to take up the slack when mounting a double socket on an uneven surface?
A client has bought some v.nice flat brushed chrome sockets, but he bought them online & they didn't come with gaskets. They are to be mounted on a reclaimed slate tile surface, which is uneven +/- a mm or 2 here and there (he did the tiling). I know some foam gaskets like this do come with some "posh" sockets like this, but i have drawn a blank finding just the gaskets for sale on their own. need for switch plates too.
Any help much obliged.

 

[morph]

flat sockets on anything other than a totaly flat surface will look crap even with gaskets, why people buy them is beyond me.

 

[mogga]

they look fantastic on flat walls but a wee distortion of the wall and they look like a dogs dinner even normal kitchen tiles make them looke like mince

 

[Knobhead]

I know it’s a ball ache but couldn’t you make your own from adhesive backed fire resistant foam. The stuff I’ve used was a near slate grey. Pity the job I used it for was switchgear painted Battleship grey, it stuck out like a sore thumb.