This is the kind of thing I typically do with grasshopper, or a script. Here’s an example of a python script that selects all items with the same area as the first item selected when the command is run:
#Get a reference to the document
doc = Rhino.RhinoDoc.ActiveDoc
#Get all the objects in the document
objects = doc.Objects
#Get all the selected objects
selectedObjects = [o for o in doc.Objects.GetSelectedObjects(False,False)]
#try to get the first selected item, if it fails print a message to the command line
firstSelected = selectedObjects
print "Select an object and re-run command"
#get the area of the first selected item
targetArea = Rhino.Geometry.AreaMassProperties.Compute(firstSelected.Geometry).Area
"Unable to measure object area"
#set up a list to hold all the items we want to select
toSelect = 
#for every item in the rhino document, try to get its area and compare it to the target area
for rhObj in objects:
area = Rhino.Geometry.AreaMassProperties.Compute(rhObj.Geometry).Area
if abs(targetArea - area ) < 0.01:
#for each item in the "to select" list, select it
for item in toSelect:
Hope that helps!