Dear Rohini,
There is no way by which you can acquire his / her shares.
Untill unless the shareholder is not ready those shares to any other party such shares can never be purchased or acquired.
I give you an example, even if the company gives an option for buy back of shares to its shareholders, the holders which accepts the offer only will give their shares upon receipt of the requisite consideration. Otherwise company can never compel a shareholder to transfer his / her shares be it listed or unlisted.
Views of other members are also solicited.
Thanks and regards
Deepak Maharishi