I would spend hours trying to find an SKU # for products that were on clearance at Walmart store until one day I realized it was right in front of my face.
Go to Walmart.com and search the product you are looking for. When it comes up click on the product and in the browser (the last 9 numbers – ask shown in the red box) will be your SKU #.
Use that number to search the inventory on Brickseek in your area. Just remember Brickseek is NOT always accurate, most times it’s not accurate at all. At least that has been my personal experience of late.
Here is a photo below for you to see a demonstration.