I have done some searching around for pharmacies that are still offering rapid COVID testing since the two I had selected no longer offer the service. I wanted to find one in my neighborhood that I could walk to.
I found this link that may help you find open pharmacies. It looks like it goes about two weeks out for information:
https://www.farmaciediturno.org/ricercatamponi.asp
Also, FCO offers testing services. They request that you register, but they indicate that the registration is NOT an appointment and the wait could be long. If you choose this option, make sure you have enough time:
https://www.adr.it/web/aeroporti-di-roma-en/test-areas-at-the-airport
I continue to hope/wish that the reentry testing will go away before I need it in early May.