Catnip, a useful herb for tummy discomfort among other things, has been around as long as mankind. So wouldn't you think, say, the Egyptians made little catnip ankhs or sphynxes (I jest) for their fourfooted household gods?
I haven't found THAT out yet. But I did discover that the earliest American retail purveyor of the catnip toy was Dr. A.C. Daniels, who opened his storefront for livestock formulas in Boston in 1878. After the turn of the 20th century his line had expanded to all sorts of animals, including cats. For them he marketed toy mice and refillable toy balls, to be refreshed with a box of his Summit Brand Catnip. You can see an advertising example of the time here, from Katherine Grier's Pets in America.
If I find any photos or illustrations of the toys at that time I will link to them. Meanwhile, you should see the bewildering array of nip thingies "Dr. Daniels" still carries!