Jazce, no you cant buy them in stores yet. so far there are 2 linkstones availeble in the game, you can buy 1 "prototype" for 10000$ and you can find another 1 infront of the destroyed yureyu building
your problems might me solved in the form of the common candy, and item introduced in the next episode wich will be released today, i dont know if the candy will be availeble for you before the 2nd gym though.