Quoted from Isochronic_Frost:Use the little rubber ones from Titan.
I use the white rubber caps, and all of the pinball suppliers sell them. Titan Pinball sells silicone post caps, rings and post sleeves in many colors. I think that's where Crispin bought his to custom color his first Quicksilver.
https://www.titanpinball.com/index.php?route=product/product&path=33&product_id=52