I explain how to do it here http://linkedexpertsalliance.com/topic/how-to-find-fresh-new-clients-on-linkedin/

If you want to code it yourself, find a big list of domain names. Create a script (I use PHP-CLI) to download the homepage of all of them and look for some kind of meta tag that only WooCommerce has. Load that script on a Linode with tmux and let that run for a few hours in the background. Now you have a nice list of domain names with WooCommerce. If you want to save time, let me do it for you. If I like your service, maybe I'll sell it for you for a commission.