Walmart@Google Express - Crest 3D White No Slip Whitestrips Dental Whitening Kit - Two 40 ct Boxes $44.88 ($19.88 if you have a $25 coupon from Walmart Google Home Mini promo)
Found this to use the $25 Google Express coupon received from buying a Google Home Mini from Walmart and activating it.
Amazon has one box of these for $34.95. This is 2 boxes for $44.88.
If you have one of those $25 coupons on your Google Express account to use before it expires on 1/31, it would bring it down to $19.88 (+tax) for 2 boxes with free shipping.