Anyone know where I can get either the weights and/or the shaft adapters for the P-Tune PG313?

Ian,

Tario can get them for you.

I bought an extra sleeve with the head ( came with screw, washer and ferrule )

Weight is available as well. Recently got an 8g weight to make the head around 200g.

Mine is now around D2 at 45"

As far as replacement ferrules go, I found that the Titleist 910 driver ferrules work well diameter wise except you have to cut the reset collar

since the adapter does not have room for the reset collar.