Weistec has them but they are EXPENSIVE ($100 each): https://www.weistec.com/accessory_port_adapter_for_rivian.html
This would definitely be a good thing to have an alternate source.
FYI - My 12/23 build-date R1T Dual-Performance MAX build came with the NEW spare tire pack.
Part Number: PT00715621-B, in case anyone wants to try and search to buy/etc.
For what it's worth - I've used them in Fremont for PPF/ceramic/tinting for my last 3 vehicles (10mil XPEL on my last offroad vehicle.)
They do good work, but be sure and check for wrinkles/fitment/etc.. They'll fix everything with no problems, but they are human and have missed stuff. We had...