I recommend you to stick to convention and patterns and use the cart icon. Users seeing the cart icon instantly translates it to "That's where I put the products I want and check out". Much like a supermarket. The shopping cart logic instantly translates to whatever products whether digital or physical.
If you start playing with icons, users will simply either not find the cart (because it's not a cart and they expect the cart icon), or stop and wonder how your new icon behaves differently from a normal cart.
If you show an unconventional icon to someone, they will interpret it in infinite ways. A "Stack Icon" can mean database, server, stack of paper, layers, etc. The same argument applies to any non-conventional icon.
Here is an article talking about cart vs bag icons:
Users aren’t just used to the word ‘Cart’, they’re used to recognizing the icon too. The shopping cart icon is distinct and unmistakable. A cart has a strong connection to shopping because it’s a common object used in stores. But the bag icon is easy to misinterpret. It’s not an icon that has a distinct shape or meaning. This makes users uncertain when they look at it.