this was the chain i used
https://www.amazon.com/dp/B005CMU84Y?psc=1&ref=ppx_yo2ov_dt_b_product_details
Radpower has 20x3 tires.
https://www.radpowerbikes.com/collections/replacement-parts/products/cst-big-boat-tire-20x3?variant=39441026023520