I am not sure if the machines still exist. But I have seen those being offered in Japanese Sex shops, for example in the Akihabara District in Tokyo. However, there is of course no telling if they are real. I can very well imagine that these are just normal panties, claimed to be used.
For the vending machine itself, there are two things involved here: A vending machine (自動販売機) and a vendor of used girls clothing. Those include by the way also school uniforms etc (ブルセラ). Or simply "pants selling vending machine" (パンツの自動販売機orパンツの自販機) If you want to scour google search while using translate, you might find something. I went through a couple of search results and could not identify any clear hint of this still existing.
