Ebay and Amazon will have what you need - thousands of options. I bought some recently for the rather corroded ones on my NBLs. Indistinguishable from the originals except for the lack of rust!
If you can, think about having only 3 spikes per speaker/stand.
3 is a “milkmaids stool” it won’t rock.
I have three spikes on my own custom built speakers, 2 at the front are used for side to side level adjustment, it’s just so rockless solid.
Go to your local dealer and see what’s on the speakers he sells. At least B&W will sell you spares, so you could try those, but I’m sure many other brands will as well. Just need to find the ones that suit you.