I always used to forget mine too! I found this pouch of 10 bags on Amazon (I know amazon is awful, but I bought these before I realized how awful they are) but they were a game changer for me because they roll up real small and have a built in elastic band to keep them in place so now I keep 4 of them in my purse so they are available at all times! It even comes in handy when I'm not at the grocery store, like if I'm at my friend's for dinner and I get leftovers I'll whip one of my bags out of my purse and use it to carry stuff

BeeGreen Reusable-Grocery-Bags-Foldable-Machine-Washable-Reusable-Shopping-Bags-Bulk Colorful 10 Pack 50LBS Extra Large Folding Reusable Bags Totes w Zipper Storage Bag Sturdy Lightweight Polyester Fabric https://smile.amazon.com/dp/B07XFLT4TS/ref=cm_sw_r_cp_apan_glt_fabc_D587MQWSF8NF2AXZKSM6?_encoding=UTF8&psc=1