First, I think we need to clarify whether or not you really are in need of baptism. You identify as a Christian, but you state that you haven’t been baptized and in fact declined baptism in a Protestant church. If you have never been baptized, then in the Catholic view you are not a Christian. You may hold Christian beliefs, but baptism is what changes a person into a Christian. On the other hand, if you ever have been validly baptized, then yes, you’re a Christian but you cannot be re-baptized in a Catholic ceremony. Baptism is a one-time sacrament that cannot be repeated. You would be received into the Church and confirmed, but not baptized.
Once you get that clarified, the next step is RCIA. In many Protestant communities, the new believer is hustled through initiation in short fashion. But the Catholic Church believes that baptism and/or reception into the Church is a serious step that—when undertaken by someone of the age of reason (around age seven)—requires preparation, reflection, and an indication of commitment. That is why adults who want to be received into the Church are asked to go through RCIA.
If you want to become a Catholic, I urge you to be open to following the procedure given to you by your local parish. It could set an extremely poor precedent for your Catholic life to insist upon taking shortcuts. As the deacon told you, desire for baptism can be sufficient should anything happen to you before baptism. And, should unforeseen problems arise necessitating baptism, exceptions can be made. But you should still do your best to cooperate with your parish insofar as possible.
