please help i need engine

i am in need to replace the engine mine still runs and all but it has this loud knock like a piston fell apart or something i dont know. i have a 95 sunfire gt i believe it has the 2.2l i was wondering where i could find the same engine or one that would fit my 5 speed tranny at a resonable price or if anyone has one for cheap i need in working order with fewest miles the better. please let me know asap and thank you.