FWIW, as everyone gets a different story from different employees at Rivian, I've spoken with multiple Rivian employees about this and was told:
check your local market to see if anyone is selling? I see many people are switching from 21" to 20" and have their used 21" for sale. I just bought one 21" locally here in Dallas for $500 with tire that still have lots of thread life left.
Call number shown on the product page. Explain to them you had received email from Rivian when they announced removal from configs—and stating that you’d be able to buy removed items from the shop at same price at later date. They will explain pricing will be adjusted by the service side, but will make a note of it. Once service processes your order, they may ask you to provide a screenshot of said email (include header showing date). You add it to the service ticket that would have already been created soon after you placed the order. Then, before service appt date, you’ll be sent a work order estimate to sign. Double check price before you sign. If price has not been adjusted, call number on product page again. That service generalist will ping local service center to have work order revised and resubmitted for your approval.
Not sure where you sourced your $450 figure. For the 20" AT spare kit, it was $800 at time of removal from my config. Gear Shop page. The page for the full size spare. You probably don't need to wait after delivery. Call the number and find out.
Oh you have R1S. The compact spare should include jack kit. https://rivian.com/gear-shop/p/compact-spare-tire. "Tire service kit inlcuded"—that's what it means. And, "Compact spare tires will be available to order in fall of 2023." It isn't available yet. They are running late.
