Looking for a plastic switched lampholder

Group:

I've got some table lamps with switched white plastic lampholders. They're currently fitted with UK-style bayonet fittings and I want to change them over to US-style Edison-screw type fittings. However, I really need to keep the style of the lampholder the same. I've been looking for white plastic switched lampholders everywhere and can't find them. Here's a pic of what I'm after:

Cheers

Den