+1. Getting this may take time, 3s would have to order it from atlas. Get only genuine orings. Orings should be coated with compressor oil during installation.
And to what was mentioned before about changing compressor oil 5-10k. That isnt correct. There isnt a schedule mentioned anywhere where it says this.
3s will have the proper repair manuals for all their models. It will mention firstly what type of compressor oil to use. It will say how much to pour in if a leak happened, how much to add if you change a pipe for eg. etc etc. While things are opened you might as well drain out whatever compressor oil is in compressor and add the same quantity back.
You can also possibly identify a leak point. Check connection points. There may be oily residue around it, that being the compressor oil that leaked out with the gas.