I have two cameras with leather bellows in nice condition and I want to keep them that way. Specifically, I want to prevent the leather from stiffening up.

Are there any particular creams or oils or dressing products that people use to keep bellows leather supple?

(Many leather care products are designed to dry quite hard to protect the leather, but in this case we don't need abrasion protection etc, we need softness/flexibility, which is why I am wary of using generic shoe or saddle products.)