If you can live with not being able to see the powder level, some heavy wall PVC will do the job.
Just trim the end that fits onto to measure funnel and yu can have as large a hopper as you like.
I recently saw one that was made from a plastic, one pound powder container. I should have looked closer to see how he mounted it in place. The bottome had a large hole drilled into it for filling.
The fellow loads a lot of different cartridges so the "make do" hopper would have to be easily removed and replaced.