Quick answer: Five days after launch, Windows Central reports the $1,299 ROG Xbox Ally X20 and its $2,499 bundle are sold out at Best Buy and ASUS.com.
If you were planning to grab an ROG Xbox Ally X20, you may have to wait. Windows Central reported on October 20 that the $1,299 handheld and the $2,499 anniversary bundle, which adds XREAL AR glasses and a dbrand case, are both sold out at Best Buy and ASUS.com. The X20 went on sale October 15, so that's five days.
Windows Central says October 20 was simply the first day it checked stock, and a Reddit thread suggests it sold out over the weekend. Preorders opened back on August 25. Windows Central points to limited production and finite inventory as one likely factor.
For comparison, the original ROG Xbox Ally X is still available for $999. The X20 keeps the same Ryzen AI Z2 Extreme chip and 24GB of RAM, with slightly faster memory, so performance is very similar. The main changes are a larger 7.4-inch OLED HDR screen, an 80Wh battery, TMR sticks, a new D-pad and a faster microSD Express slot.
The X20 isn't the only pricey handheld that's hard to find. Windows Central says the $1,799 MSI Claw 8 EX AI+ also sold out within days and is still out of stock at Best Buy.