Amazon uk has Mario Kart Live: Home Circuit available for preorder. It costs and additional 6ish bucks for shipping. Price drops down to £83.32 (106.69) when shipping to the states.
Amazon uk doesnt charge you until it ships, so you can always cancel your amazon pre order if you get one when Amazon US starts selling them. Personally I think this is going to be one of the hardest Nintendo related items to get due to its oddity.
Luigi Version - https://www.amazon.co.uk/dp/B08HF78VS8 [amazon.co.uk]
Mario Version - https://www.amazon.co.uk/dp/B08HF7PBLJ