I too had trouble finding these switches! I ordered them loose from ebay and soldered them into a modern board. I like them, but not enough for everyday use; they are just a little too rough-feeling for me, although not as rough as something like black Alps switches. They've got a nice bit of tactility, but are a little too stiff for me as well. These are good enough switches that I'm certain they are some folks' favorites, but I doubt you can know if you like them until you try them. I should mention that my switches were brand new; I have a ton of used MX brown switches that are filled with dust & scratchy, so I suspect it's hit-or-miss to buy them used.
I for one have not noticed any pinging when using clears; but then, I love the IBM model M, so I may just not notice a weaker ping sound.