Where are you? Are you in the US, Canada, UK, . . . that will help with finding gravel and fish.
What are the fish in the tank with the sand? He'll like sand much better if it smooth grain, has nice tankmates and similar water. Mine swim like mad when they are out. Usually up and down the tank sides in their loachy dance.
I could be wrong, but if you can't find his species, buy any Pangio (any type of Kuhlie). They all get along and like hanging together. I have five species together and they all hang out. I have a hollow piece of bogwood and you'll see the nose of a P. oblonga, a Kuhlie and eel Kuhlie loach sticking out together. Very cute. They all dance together, sleep together, eat together. . .