A very quick and hopefully easy suggestion this time.
Might it be possible to add to his greet prog an offer to let PCs see what he has for sale even after they have completed his quest? As it is now, he gives a hint to the keyword, as far as I can tell, only if one has not done the quest, which makes it difficult for some players to return later and get another of his goodies. And those are some nice goodies to miss out on!
Thanks for reading.