Hi Stephen, I am aware that these springs would probably be to large for your project, however when I built my 10" Reflector many years ago and to hold firm the main Mirror I used old car engine valve springs.
They are very high strength and are perfectly machined flat on either end to sit squarely on any surface.
They would be to large for your job I expect but there are millions of them of different sizes at any car wreckers, well they were when i needed them.
Leon
