Sean, the place near Chicago you are likely looking for:
Controlled thermal Processing, Inc.
703 Rogers Street
Downers Grove, IL.
This is the company I was involved with in 1998, doing my (factory sanctioned) cryo experiments with Benz Micro cartridges. Having now done experiments with four different cryo facilities, NASA is absolutely the superior vendor
Their tanks are designed in compartments and computer controlled. The time and temperature of the treatment has evolved from need to treat the tiles on the nose of the shuttle, to door latches and electrical components.
Realize that everything NASA launches faces the extreme cold of outer space. They must pretest and treat all earth bound parts to avoid a catastrophe
The Hubbell outlets I offered were treated there, and as other items I have had done, the more absolute the treatment, the longer it requires before satisfaction with end results. My experience has been that the difference is worth the wait.