Question
It is a disruptive and niche startup with an initial market of 4.5M. Scalable vertically and horizontally. Top category, such as food and technology. But without traction.
Answer
I like David Favor's approach: Bootstrap if you can and raise money only when you have to.
If you do need the cash, however, convertible debt allows a softer approach to valuation than selling equity. Please let me know if you'd like to discuss further.
Best of luck.