Recipe for starter

I have been reading some of your conversations about the sourdough bread starters using the potato flakes. I have a starter that I feed once a week with 3 Tbls potato flakes, 1/3 cup sugar and 1 c of water every Saturday night.  I have been working with the same starter for almost 30 yrs.  It has finally stopped bubbling like it use to and I think its time for a new starter.  However, the lady I got it from has passed and I don't know how to make a new starter.

Can anyone help me with this. I love making my bread and sharing with my family.  It has gotten to be a tradition.