if you are using steel shelving you can use the dog cone anti lick type collars on the bottom to stop pests( mice rats from climbing won’t stop bugs. the collars can be made of any material but i use plastic or metal both seem to work fine just have to be at 6 inches off ground at the bottom and at least 6 inches taller at a 45 degree or closer to the main pole i have heard people using pvc pipe to cover legs for a 12 inch section too slick to climb. seen rats climb 12 feet verticle on a stucco house wall so steel shelving not a problem at all.
go to a housing recycle store we get ours there since Mylar packed the buckets only need lid and food grade. get them with lids for $1 each just need to wash but i do that anyways before food packing.
if buying a lot you can call local ropak rep and get a bulk deal on a pallet worth of buckets.
The only thing different in HDPE food grade is the type of chemical used for the release/anti stick chemical. if using mylar it should not penetrate the mylar to contaminate the food if washed using soapy water as it is a surface treatment of the plastic not an embedded chemical as far as my knowledge goes on it.