What's your budget?
Many major retailers carry iP4 docks. Target, Sams Club, Costco, Best Buy, Walmart, and even Bed Bath Beyond. Check the boxes to make sure they're iPhone compatible. Apple stores have them too, if you happen to live near one. Theirs tend to be pricier, but you know they'll work. Most those places carry name brands like Philips, JBL, Bose, and Sony for under $100 ('cept the Bose obviously).