Ask HN: How to fund a small idea

I'm a fairly experienced software engineer. I have a small hardware idea that I know I can execute really well on and would be very well received by the small community that would use it. I'm fairly certain this product won't expand the existing market, just solve a really tough problem this market has been trying to crack for a while.

The lifetime value of this product, given the market, is reasonably $10 million dollars in the US. I'm being very stingy with my estimate, but this market would never, even globally, crack $100 million (probably not even 50). I know this is exactly the kind of thing VCs AREN'T looking for. Let's say I need an initial 100k to get going, and no more than 500k over the lifetime of the company. What are my options how can I get this kind of money for such a small idea?

tldr; How do you raise a small amount of money for a small payout?