More items will be introduced in the future. And PRO is not a battle simulator where you can use your desired Pokes and Items anytime you want. You gotta put some efforts to build a decent team that can overpower your opponents. One of the factors that makes PRO PvP competitive is the efforts you put to get Items, Pokemons, and Moves. Unlike leftovers and berries, Focus Sashes can be really dangerous if used by Pokes with high damage but low defense which are supposed to faint in one hit. Considering its effect, we intended to make it rarer, while on the other hand it's not really impossible to stock it up.
I think it would be nive to have a quest or evenement who can drop Focus shash more frequently. That could be a difficult Quest for experiment player. ( like boss lvl 130 with no items or potion alowed. )