I don’t know what exactly you are looking for; in this chapter we understand that St. Paul is addressing the Jews who think that by their circumcision they are justified. He clearly states that one must be circumcised in the heart and continue to do good. Here is a scripture which clearly demonstrates that baptism is necessary as commanded by Christ Himself.
19 Go, therefore, make disciples of all nations; baptize them in the name of the Father and of the Son and of the Holy Spirit,
St. Paul here is talking about those who are trying to be justified apart from Christ by keeping all the Mosaic laws, which included circumcision. His whole point in this chapter is that the Old Covenant and its laws have no power to save us, because Christ fulfilled it.
It doesn’t follow that because the old circumcision is useless, therefore baptism is not necessary for us, because baptism is part of the New Covenant, not the Old. It’s the new circumcision yes, but Jesus is also the new Passover lamb, and our new high priest. The old Passover lamb and the old high priest aren’t necessary anymore, but we shouldn’t reject their new covenant fulfillments. The whole point of the New covenant is not that it abolishes the old, but fulfills it. (Mt 5:17) All the signs of the Old covenant were shadows pointing toward their ultimate substance in Christ. (Col 2:17)
If we reject the substance and go back to the shadows, we can’t be saved. And that’s Paul’s whole point. Not that the substance itself is pointless.
Most importantly though, Jesus is the one who instituted baptism and told us of its necessity. (Mk 16:16, Jn 3:3-5, Mt 28:18-20) And we can’t just ignore his words.
You are reading the scripture out of context. The new covenant found in the New Testament basically replaces the old covenant found in the Old Testament. The first so called converts were jews which means according to their religion, all boys had to be circumcised. The necessity of this practice was put into question as gentiles were also converting into Christianity. If memory serves me right, Paul was working with the gentile converts while Peter was working with the jewish converts. The question arose did the gentiles have to be circumcised like the jews or not? It created a big conflict which is seen in the book of Romans. The answer was: no. I think circumcision gradually decreased at least in Christian practices and it isn’t part of the faith. I think it continued to be used due to other health concerns.
John the Baptist baptized Jesus which began the practice of baptism. To be baptized, one is anointed by water and the holy spirit. Baptism is a sacrament that all Christians believe in. It is part of living the Christian life. I don’t understand why you would want to refute the need for baptism when baptism is part of Christian living but circumcision isn’t.