Sears has a few Craftsman mower blades on sale. The blade I need is still near full price, but I hope this helps someone.

Craftsman 21 In. Mower Blade $9.99
http://m.sears.com/craftsman-21-i...133524000P
non-mobile
http://sears.com/craftsman-21-in-...133524000P

Craftsman 21" Precision Cut Lawn Mower Blade $9.99
http://m.sears.com/craftsman-21in...133521000P
non-mobile
http://sears.com/craftsman-21inch...133521000P

Craftsman 22" Lawn Mower Mulch Blade
$9.99
http://m.sears.com/craftsman-22in...133256000P
non-mobile
http://sears.com/craftsman-22inch...133256000P

Craftsman 21" Advanced Mulching and Bagging Blade $14.99
http://m.sears.com/craftsman-21in...133058000P
non-mobile
http://sears.com/craftsman-21inch...133058000P

Craftsman 46 in. Hi-Lift Tractor Blade $11.99
http://m.sears.com/craftsman-46-i...133285000P
non-mobile
http://sears.com/craftsman-46-in-...133285000P