How to switch between brands with formula shortage?

We usually use Members Mark gentle infant formula. We can’t get it or enfamil. We managed to find one can of earth’s best gentle formula. I have to buy what I can find. Is there a way to go about switching between brands with this shortage?

Baby boy is 5 months on Tuesday and has been baby led weening as well.

I want to be as gentle as I can on his tummy.