To be frank, small retail listings in strip centers can sometimes be the most difficult to lease depending on the quality of the strip center.
Can you tell us more about the center? What's the access (ingress/egress) and visibility like? Does the center offer signalized access? Or is it mid-block with right-in/right-out only access? Are there any national tenants or are they all mom & pops? How many SF is the center? Is the center parallel to the road or perpendicular? Traffic counts in front of the center? Is the center surrounded by other retail?
Regarding finding tenants, Costar can be good but also expensive. To be good at small store retail leasing, you really need to be out in the market talking to the retailers. For you, know what categories are missing at your center, and then get out there and hit up as many strip centers as you can in a +/- 3-5 radius.
Do you have a stock proposals/LOIs to use? Do you know what main points need to be covered?