Current XR/CRF80/100 and TTR125L tire options

My shop guy says the BT-45's are becoming less available, as far as size options, in the V speed rating, which is supposed to be the preferred compound. He's saying the BT-46's are their replacement, but also have limited sizes available, currently.
Just getting started with a stock TTR125LE, and an XR100 with a 16" front borrowed from my dirt XR80.
Recommendations for the preferred sizes currently available, please?