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!
I went ahead and ordered a pair to the US.
Hopefully they a) Work with the global headset and b) VRChat supports them (I'm sure that's a matter of time if not).
I'll report my findings here.
UPDATE: They work! VRChat does not support them as of this writing however.
https://youtu.be/I9Uqg1a80BI
๐ซก
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.