Yes – they can be very hard to track down. I’ve had a few of those Kendas for a 14″ wheeled bike (not mine!). Initially got them from a bike shop closing down sale and then had a hell of a job finding a replacement when one got skidded through.
Found on ebay in the end (for a lots less than the link above) – so worth hunting. I found googling with a few variations on “Kenda 14 x 2.125 tyre tire” etc worked eventually.