Most times there are hirelings that allow you buy and stow potions with their respective dresses, otherwise there could be hirelings in guildhouses which have a dp allowing to stow them aswell, or at least there could be a house with a trader hireling close to dp, so these should be your first option almost always, yet if we don't take into account house with hireling (because not all city have one accesible for everyone) you have:
Several npc really close to dp (some take less than 20 steps):
-feyrist -Talila/valindara
-Moonfall -Sundara
-Silvertides -Nipuna
-Alaistar -Rathetlon
but if you want one where you don't need to make extra click/walk (stairs)
then your faster npc should be nelly in svargrond
since you need to only perform one click to reach her and is closer than ghorza and other direct npcs