What to do if there are no similar Comparables on square footage

[Curtis Daniels]

I have a great way of bringing up comparables, but when I do, I often see that the other houses with the same bed and bath don't have the same square footage. For example 

3744 Wabada dr. Kirkwood Missouri: 

Has  2 Bed, 2 Bath and 675 Square footage 

3 other houses with the same number of beds and baths have twice that size: 1240, 1135, 965 sqft. 

What do I do when I don't have good compables on the square footage? 

[Joshua Springer]

If you can find something similar age, neighborhood and condition you could use $/sq. ft...see if that is similar between the others...it could give an ok ballpark.