Yes! The approach I took was to build a product that solves a broad problem (in my case geographic visualisation) and showed that to get clients who wanted something similar but tweaked for their use case. Of course they then ask 'is it possible to do this other thing' and all of a sudden you're doing data vis consulting.

As an aside, I'd suggest selling the data science too if you have the skills since data viz isn't just about showing data but figuring out how to show it to answer the relevant business questions - they go hand-in-hand and it's both a more compelling sell and adds more value to deliver the full stack solution instead of just the viz piece.

Good luck!