Can This Fitting Be Replaced

I found the leak in my York R206R compressor. In the picture below soapy water shows the leak is right at the gasket at the low side port pointed out by the arrow. Is this part replaceable?
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This may have been a false alarm. In looking for the fitting and speaking with a salesperson on line, I put a wrench on the lower nut to remove and photograph it so he could identify it and found it was loose. Recently I changed the timing belts and moved the compressor over. Evidently this loosened it. I should have thought to check this sooner because the AC worked before changing the belts but failed to come on after the belt change due to low pressure in the system. Quite a coincidence, I'd say. At the moment the system is pressurized with air to 45 psig and so far (1 hour) there has been no movement in my gauge set. I'll let it be for a day just to make sure but I think that was the problem. Prior to tightening the nut, the pressure would fall about 5 psi per hour. If this is the only leak source, all I have to do is replace the receiver/dryer and recharge the system.

 

Hate to sound too ignorant but where are the O-rings? Is the dark portion just under the arrow an O-ring for the suction side? Five years ago I replaced the shaft seal but disconnected the compressor at the hoses. It has been a couple of hours now since I charged the system with air and the pressure has not dropped at all. I am beginning to feel confident there are no other leaks. But as you suggest, I'd like to replace the O-rings.

 

I filled it with air to test for leaks because there is no sense in wasting refrigerant. Once I am convinced there are no leaks, I'll change the receiver/dryer, pull a vacuum, and recharge. The reason why I pressurized it with air instead of evacuating it is because the air test is more severe. I pressurized to 50 psig and so far it is holding. Had I only evacuated it, the pressure difference would only be 14.7 psi. Big difference.

 

I do not have a nitrogen source and planned on replacing the receiver/dryer anyway. But, hey, air is 72% nitrogen. ;>)

 

But wait, wait. My compressor has a storage tank as does my pressure regulator which has a small tank attached. Both have to be periodically drained to remove water that has condensed when air is compressed. Both tanks are always under 120 psig pressure.

Anyway, my vacuum pump will get most of the water and the new receiver/dryer will hopefully get what remains.

But I'm still wondering about the O-rings at the compressor head.

 

Object is to see if the system leaks. You can attach a vacuum pump along with gauges and see if the system loses its vacuum. But in that case you only have a driving pressure of 14.7 pounds per square inch to check for leaks. I choose to pressurize the system to create a considerably higher driving pressure to check for leaks. The fact that I introduced water vapor into the system by pressurizing it with air is no problem because I'll evacuate it and replace the receiver/dryer before recharging. As ferrariowner wrote it would have been better to use nitrogen, but I do not have compressed nitrogen. So air will have to do.