lee valley usually has sets of the larger diameter (not porter cable size) for around $20. My 1 in, 3/4, and 1/2 see the most use.
http://www.leevalley.com/wood/page.aspx?c=2&p=41778&cat=1,43000,51208&ap=1
http://www.leevalley.com/wood/page.aspx?c=2&p=41778&cat=1,43000,51208&ap=1
