Kirkland Signature Diapers on Sale at Costco (2022)! by Rhonda April 4, 2022 April 4, 2022 *UPDATE* 3/25/22. Kirkland Signature Diapers from Costco are made with plant-based materials and are soft, absorbent, and hypoallergenic. Prices have gone up for all diaper sizes but good thing they… 0 FacebookTwitterPinterestEmail