Used Helium Leak Detection Equipment

Try http://www.emcgrath.com

Try www.hindhivac.com

Bite the bullet and purchase a new leak detector. In the long run you'll be better off. I have purchased used and they're nothing but trouble. Purchase one with a turbo and no LN2 trap. If you don't need it for other things, consider having the testing done by a third party.

I don't mean to discourage you, but you should be aware that if you plan to expose your potted switch to helium pressure and then leak test it, the potting will likely have absorbed some helium. During the test, the helium will desorb and give a leak indication on a properly sealed switch. This is a fundamental property of helium leak detection and the reason why it is almost never used to test plastic materials, or containers that are coated with organic material.

Well said and very true if the article is to be "bombed". However the buyer should know that and it may be why the leak rate is so high.