Cost Effective Clay?

Can anyone recommend a cost and safe clay to use for internal use. I have been using Yerba Prima Liquid Bentonite but find I am going through a bottle in a little over a week. So at 16 bucks its getting expensive.

I need a clay that is good for internal use as I dont care too much for the baths as they are a pain in the butt to clean up.

I really like the Yerba Prima for ease of use but I need to think of finances at the moment.

Thanks so much in advance.