If you are in the US, you probably already know who the players in your area are and can approach directly. Frankly though, the small number of firms and positions is a sign it’s time to change careers.

Being a specialist field, networking is probably the most effective approach.

The other alternative might be to go to the specific company's HR careers pages. It's not like there's hundreds of potential employers.

Would depend a lot on where you live I expect. Do you live anywhere near Eindhoven ?