Looking for 28" or larger Used, SoCal

I have been riding for almost 50 years (boy are my legs tired, budamb, bump) New to this forum. Have just started riding my Columbia 20" again for the exorcize and fitness. Looking for a good deal on a 28 or larger. If all goes well I may move up to a 36 with all the bells and wistles some day.
Located in Orange County
thanks
Dave