The manual has the spec on the mic - it's 2K Ohms impedance. That should at least help point you in the right direction?
For the grey seal pads, I'm sure you could get the directly from Yaesu. They also come with the bluetooth option. I suppose you could use something like aluminum foil tape also, which can be found at most hardware stores.
DO you have this battery: 2000mAh FNB-102LI Battery for YAESU VERTEX VX-8R?
My thf6 has a 2000mAH stock.