Valve announced on February 15th that iFixit are now Valve Index and Steam Deck official replacement part sellers.
At the time of writing, iFixit does not have any replacement parts listed, however we expect that to be updated shortly.
Valve announcement:
https://store.steampowered.com/news/app/1675180/view/4347665658888576968
iFixit Valve Index page:
https://www.ifixit.com/Device/Valve_Index