Mazda finally confirmed there will be a MX-30 REX in US in 2022. This is the only other vehicle with a REX, although they call it a PHEV. Since i3 is discontinued this will be the closest alternative in US market.
https://www.mazdausa.com/vehicles/electric/mx-30-electric-hybrid
https://www.mazdausa.com/vehicles/electric/mx-30-electric-hybrid