There are many alternate circuits,but wether they are better or not depends on your application.If you are just driving an 8051 circuit then there is not much advantage in using different configurations.
Yes there are four pin oscillator units available in all standard frequencies,many manufacturers make them.Containing all you need to provide astand alone oscillator,as to where to get them,dunno,try the major distributors,I think that most have offices in india.