Where kind I buy solid rubber tubes for bicycles?

I seen a bicycle at the store I want to buy, it has 28 x 1.75 tires (700 c) and I want to install the same size solid rubber tubes in it like no-mor flats. But the stores only has no mor flats tubes that only go up tp 27 x 1.75. Does anyone know of a place online that sells this size? 28 x 1.75 or (700 c)