Greetings, I had a friend ask where he could buy some 3x3 pine
approximately 4 ft in length. He said he went to a hardwood store in the
city and they didn't have it. I've seen lots of pine furniture and
bedposts, so someone has to sell it. Any suggestions? THX

Suggestions? Sure - laminate smaller pieces or plane down larger ones.
A local cabinet shop or hardwood dealer may do the planing for you for
a price.
The posts on the bed frame I'm working on are 3 pieces of 5/4 oak
laminated together - final size is about 3 3/4 x 3 3/8.
Good luck,
Andy