Im trying to find a list of CFO's (emails too) working at tech companies or digital agencies where there is more than 5 employees. What is the best way to get this specific info, apart from buying a linkedin premium subscription and trolling the search.
Her are a few options that might help:
https://discoverorg.com/
www.lead411.com
If I were in your shoes (assuming you have a little bit of budget), I would pull together a list of target companies. This can be done pretty easily, as their are many public databases of companies you can scrape (eg. Inc 5000).
Then I would have a low cost freelancer from Upwork find the CFO or finance decision maker for each company. You'll pay around $3-5 per hour for this kind work, and a freelancer can usually find around 30 leads per hour. It's a very cost effective method.