SSL both ensures encryption aswell as authenticity of a site or business trough certificates.

The Certificate present on the https://checkout.lookingglassfactory.com/ store is "Let's Encrypt" which is an automated way of doing certificates with zero accountability, eg. not something I would want to fill my creditcard details.

Most phishing use "Let's Encrypt" and if the site is ever hijacked there is a good chance the same will be used here.

Consider installing a regular or EV certificate.

(Extended Validation aka "a business certificate" being most suited for accepting credit cards info)