Tell me if you have been in this situation before: you're in the inn - because that's the only place you can use the glamour dresser - and you're making a new glam. This time though, outside of your usual dyes that you carry on you, you decide to experiment thouroughly with colors you've rarely worked with before. You finally pick one but unfortunately, you have to run out of the inn and travel to god knows where (if you're lucky, the dye you want is in the city state you're already in) just grab one or two and then run back to finish things up.
I think the glamour dresser needs a dye seller that somehow sells you any dye. You would still have to use the correct currency (like for example, gunmetal dyes can be bought only with fete scrips and more recently, island cowries) but at least, it'd be there for you to use within the immediate vicinity.
Now my first bs excuse to reason why there's a dye seller in the inn that can sell dyes from anywhere would be "allagans" but they've been overused to just about explain anything. Maybe Cid comes over and installs an Amazon style mammet that somehow connects through some aethernet.
Or just put a Super Dyemonger npc. Thoughts?