I've never heard of frozen or pre-killed crickets, or any kind of insects for that matter, barring freeze-dried. I would just buy them or breed my own, it's not hard. Better yet, breed dubia roaches. I've been told they're much healthier, and I can vouch that they don't smell, breed like mad, and pretty much thrive no matter what, even with some neglect.
How on earth DO you pre-kill a cricket anyway????