Actually, I thought 'jack plugs', so I claim a near miss, in spite of my 'not a clue'. Screw anchors might work about as well.
But, about the big round pieces, I've got some 'electric wire fence insulators' that might work, Sean. I'll go looking for them.
Fair warning: dangerous expeditions to the basement have been disappointing of late.
Funny how everything in shapes like that makes me think of the Regula One station.
Doug