These are easy to make and not very expensive. ( I sell them locally with battery for $20) I took an existing design and modified it some by using 3300lb epoxy to reinforce the circuit.
For a link to other pics
https://www.facebook.com/photo.php?...223.1073741831.321888721288929&type=1&theater
For a link to other pics
https://www.facebook.com/photo.php?...223.1073741831.321888721288929&type=1&theater