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!
Update: These now work with the latest version of Pico Connect and SteamVR = Full Body Tracking in VRChat on PC!
You’ll probably need the latest firmware version for your headset.
You may also need to install the Chinese version of Pico Connect version 10.15 to enable FBT and then install a newer Global version if you do choose.