Brachylog, 16 bytes

;I×≜.ẹḅhᵐc~a₀90∧

Try it online!

This is pretty slow

###Explanation

;I×≜.              Output = Input × I
    .ẹḅ            Deconcatenate into runs of consecutive equal digits
       hᵐ          Take the head of each run
         c         Concatenate into a number
          ~a₀90∧   That number is a prefix of 90 (i.e. it's 9 or 90)

Brachylog, 16 bytes

;I×≜.ẹḅhᵐc~a₀90∧

Try it online!

This is pretty slow

Explanation

;I×≜.              Output = Input × I
    .ẹḅ            Deconcatenate into runs of consecutive equal digits
       hᵐ          Take the head of each run
         c         Concatenate into a number
          ~a₀90∧   That number is a prefix of 90 (i.e. it's 9 or 90)