What would be a stable way to hold lithium hydride powder? I currently have 100 grams of lithium hydride powder that needs to be held in a solid form. Initially, I was considering using cement, however, the moisture require converts the lithium hydride to lithium hydroxide. What would another moisture-free agent be that I could use for this task?

If it helps, the lithium hydride and the solidifying agent are to be used for neutron moderation.
If the LiH needs to be exposed to ambient conditions, it should be enclosed is a moisture-impermeable container, e.g., a glass ampoule which is closed off. Glass can be blown quite thin - but then you need to be quite careful. As DrMoishe suggested, PE or PP would be good, but I'm thinking of it as a closed tube, not as a binder.