Do you really want to restrict yourself to meeting people in their 20s ? If you expand your horizon a bit, plenty of exciting founders in their 30s,40s or even 50s .
Maybe the institutions near you do the same, I am sure your input would be invaluable there and also the (future) founders would be right in your age range.
You can try milling about various startup accelerators, I guess. You might find a few who did what you did, and they tend to have a younger crowd.
BTW, did you consider applying to YC? You don’t have to move permanently to SF to join.