Assistance with finding and replacing the top sash lock

Thanks for contacting us, Azam. It looks like you have the old discontinued Silverline Swinger window. While this window isn't made anymore, we still carry hardware for it.

The black nylon piece you show in the first photo is a piece broken off of the 18-027 tilt latch. This serves the double purpose of holding the balance down, like a top sash guide. You need to raise the sash if you can, or try to lower the balance back under the tilt latch. 

Once the sash and balance are aligned, you can try to raise the sash up to the 16-009 take out clip to disengage the balance. Then pull back the tilt lath and swing the sash towards you. That will allow you to replace the hardware more easily.

If you need to replace the balances as well as the tilt latch, let me know. These have to be custom made and they take a bit of explaining, so if you need them I'll go over the information necessary to proceed.