Thanks for reaching out! I hope your day is going well.
There are a few options you can try to customize your cart page to have your sale products crossed out with a final sale badge. The first option is to adjust your theme’s code and add this in manually. This, however, requires coding knowledge so you may need to hire a third-party developer.
The next option is to reach out to our theme developer as they may provide small customizations to the theme for free! For example, Shopify developed theme’s support 60 minutes (lifetime) of limited customizations. The Stiletto theme, however, is third-party. You can find the contact information for your developer in your theme’s settings.
Lastly, if the above options aren’t feasible, you can use a landing page builder such as ShoGun or PageFly. This will provide you a fully customized cart page.
In the meantime, I took a look at your site and its beautiful! One bit of feedback I can provide is to remove the ‘Powered by Shopify’ footer. This is a simply change but makes your store more professional!