Trusted Shops does not currently offer a plugin for Opencart.
However, even without a plugin, you can still use your booked products from your first day of membership. In order to do this, you will need to manually integrate your products into your website.
In the Developer Centre, you will find Opencart-tailored guidelines to help you with the integration process:
In the instructions, you will learn …
... how to integrate the Trustbadge into your website.
... how to collect service and product reviews.
… how to integrate widgets into your website to present collected reviews in an appealing way.