Greyhawk Shieldlands

There are two simple answers to the question “How do I buy stuff in Trimarch?”

1. Take a trip: get your sack of cash and your trusty steed and ride to Critwall, Admundfort or Radigast City and shop to your heart's content. It'll take time, but you'll find what you want.
2. Place an order: if you go to Fudley and meet with Marcello, you can place an order and he'll get what you need on his next trip to the city. It will take 1d4+1 weeks for the order to arrive, and the payment is upfront with a 20% service charge.