I was going to recommend
this cheap clone which I have a few of, and actually like better than the authentic A20, but they do come from China and need to have the cradles lined with felt to hold 20mm mic bodies. (I see this as a plus actually, as they bodies are thus protected from scratching.)
Honestly, I hardly use them anymore though. Rycote INV mounts are
so much better in every conceivable way that you should just buy those. Once you use them, you will find that they are
not expensive at all, given their performance and durability.