The USA ones for rubber bumpers are sort of pyramid shaped (ZKC221) and the UK ones are oblong (ZKC2251) as per the URL you put up.
Here is how I reused old rusty clips:
The biggest problem in removing these is that the nuts are rusted to the thread and when you turn them you snap the threaded rod off the plate. Having snapped off a few I then found that I could hit the nut with an angle grinder so that one face was gone. After this it is easy to split the nut off and the plate falls away.
I take the old plates and have them zinc plated again, this cleans them up nicely and removes all rust. Yes some were badly damaged by rust but many were able to be salvaged. Considering the price of new ones I found this to be an economic solution.
Jolyon