Buy what you need at a Costco. They have a fantastic returns policy. Friend of ours works at a Costco and at the end of each summer, one family returned camping stuff they bought earlier in the season so they didn't have to store it. After 3 or 4 years, the store manager figured out what was going on and that was the end of that...
Don't know if it would work for you, but you could open up an account at a mailbox somewhere at your destination. Buy some things online, get them shipped there (often free shipping) and pick them up when you get there.
