There's none sold there. Might make sense since there's the mighty wizardry tower.
<.< ...>.>
They wizard there thinks its stupid to sell EMPTY potion bottles.
Goblock dueled the fellow, and lost. So you have to win for him to sell the empty potion bottles!
Look closer, there is a seller.
Found it, nevermind.
Besides, sending PCs to buy bottles for me is actually fun.