How to gain both wisdom and wealth in the Amidah prayer

O Ch 94 (2) Mishna Berura 12 suggests that in the Amidah one who wants to gain wealth turns his face northward or to gain wisdom turns southward.

I remember having found a source that suggests that in the blessing for wisdom one can turn his face south to get wisdom and in the blessing for sustenance one who wants to gain wealth can turn his face northward. In this way one can get both advantages - wisdom and wealth.

Can someone redirect me to that source please?