These have been in beta testing for awhile. I'm not sure if they're supposed to be for sale yet but I'm seeing a few sellers on AliExpress offering them for around $60.
VRChat just released on Pico about a week ago. I don't know if support for these has been implemented yet.
Please comment if you have any insight!
Shame they don't work on quest 2 that would give me some incentive to get some for myself