A best bet is one box of Mickey's Adventures Checks for $23.99 before the above coupon,
$8.50 after. (Search under Side-Tear Checks to find them.) Even better, buy four boxes for $28.50 after the discount ($7.13/box). With free shipping, that's up to $43 off and the lowest total price we could find.
Update: Just need one box? A reader found that coupon code "TGY7" yields a price of $7.50 for the check above.