The bikes in the second picture appear to have 26x2.125, which fit the same rims as 26x1.75.
26x2.125 is all over ebay in white (and several other colors) in "small brick" (Schwinn clone) pattern and also "diamond" (Goodyear clone) pattern. There might be a Sunlite or Kenda pattern available as well. Availability has been spotty due to a general shortage of bicycle tires and parts. Some colors sell out quickly although they seem to be back in stock every couple of weeks or so.
If it must be 26x1.75, they have been made but I have not seen them lately.