Membership for Responsive Shop Theme

The responsive directory theme allows for membership. I am building a website using the responsive shop theme and I need to have the membership option in the shop theme also.

I want to be able to restrict parts of the website to paid members only.

Is there a way to add the membership function via a plugin?

I don’t want a third party plugin. I want the PremiumPress membership option as it is in the directory theme.

Any ideas would be appreciated.

Glenn