Stainless steel containers will certainly do any storage job well, and are infinitely more fail-safe compared to glass. Common kitchen containers should work. Grove bags and or 'food grade' metal foil laminated bags are also good candidates.
Rigid air-tight 'food grade' plastic containers are perfectly fine in my view to store buds long-term, or store anything else that is not wet or fluid. I presume these toxicity concerns about plastic containers are more related to leaching or what diffuses out when liquids are put in. If you use plastics to hold wet food or drinks or handle flexible plastics (relatively oozing plasticizers), you certainly shouldn't have any concerns about rigid "food grade" plastics somehow contaminating buds.