Buying mt fuji regional passes outside of tokyo

Hi
We are travelling from matsumoto to lake kawaguchi (stay 1 night), then on to hakone next day and at evening return to Tokyo.

We want to get either the hakone free pass or the mt fuji hakone pass.
Can we buy this pass when we are in lake kawaguchi/ hakone?
Or is it possible to buy at Shinjuku station before leaving to do to matsumoto and then use the pass at a later date .
Thanks