After doing some research, I discovered that there is an alternative to silica that's more effective: activated alumina. It's relatively cheap when bought in bulk and can be regenerated easily in a normal oven. I discovered others had gone down this path before me and that quite a few were using powder shakers as desiccant containers that were all-metal and therefore oven-safe. For around $2.50, you can make a super effective desiccant pack that compares with some retail options that are 8x the cost! When they become ineffective at maintaining low humidity you can recharge them by tossing them in the oven at 400°F for a couple hours.