Convert to FBA Without Losing Sales?

Hello! I’ve been an Amazon Seller for a few months. One of my products is doing great.

The last time I converted one of my products over to FBA, it took Amazon 4 weeks to take it and start selling it. In those 4 weeks, I could no longer sell the product and fulfill it myself.

How can I convert my self-fulfilled product into a FBA product without r having zero sales for 3-5 weeks? It is also 5-star and I don’t want to lose that as well.