I am going to set up one hearing aid circuit using POWER AMPLIFIER iC la4537m (see the attachment).

But in our locality this IC is rarely avail. Can anyone suggest any alternative ic to
la4537m so that I can directly replace on main circuit ?

 

I choose TDA2822M.

I can change its mono configuration to stereo easily,but- it can
only input through two channels only.

How can I configure a commercially available hearing aid circuit
that can absorb all surrounding sounds around patient within reasonable range ?

 

A hearing aid does not boost all audio frequencies. It boosts only frequencies that need boosting, usually high audio frequencies.

Your schematic is too fuzzy to see any details.