For the small lots that you are looking for, there are a number available in Riverside and Old Greenwich in R-7 (minimum 7,500 SF) and R-12 (minimum 12,000 SF) zones. I would welcome the opportunity to send them to you if you mare not presently working with a broker. Please contact me at firstname.lastname@example.org.
There is one that matches your requirements perfectly - if are currently working with a realtor, I would appreciate the opportunity to work with you. Riverside and Old Greenwich are areas that offer great family lifestyle, and are usually on smaller lots.
45 Field Point Rd
There are many properties that meet your criteria in great neighborhoods. I am also aware of a new construction property that is not yet listed. Please contact me at Carol.Zuckert@sothebyshomes.com or 203-561-0247, if you'd like more information.