SOLUTION: The lot of AM1805AQ from Ambiq arrived today and as I hoped… it is confirmed to be a 1:1 direct replacement/identical part. For anyone else searching for availability of AB1805-T3 you can order AM1805AQ directly from Ambiq Here. I ordered the supply I needed 4-5 days ago and they arrived today in the US from the the Netherlands. I was able to de-solder an AB1805-T3 from a prior board, clean up the PCB and solder on a new AM1805AQ. Everything checks out and works properly. So my immediate need is met. Posting here in case anyone else is in the same scenario.
That sure was a fun challenge to solder that tiny thing by hand. Maybe some of you seasoned electronics Guru’s are used to it but certainly was the smallest components I ever dealt with. Some solder paste, a hot air re-work station, isopropyl alcohol, flux and some solder wick were all required in this delicate process. Took me 3 tries but eventually soldered it correctly.