Have you read the related topics in this forum?
Basically when you don’t have RH control you are limited to vacuum thermical-sealed envelopes as the ones used in food storage. The most used method includes a neutral or alcaline pH paper interleaving.
This makes the enclosuring more expensive (of course is still a lot more cheaper than buying a RH controlled freezed) and changes even more the way you can access that material later since you will have to break the envelopes and have a longuer wait (in controlled conditions) until you can actually access the material. It involves also a more intense control of envelopes and seals integrity since the RH will be always 100%.