you have 2 options as mentioned to me by Saudi Embassy in Qatar as I needed it too 1. if you know somebody in Saudi ,you can ask them to get it for you,send him/her your finger print from Qatar, passport copy with saudi entrance/exit page, copy of NOC from your Saudi company, IQAMA(if you still have it).
2. Thru Qatar Saudi Embassy, you need copy of NOC (saudi),passport copy showing Saudi entrance/exit page,personal letter from you stating the reason for police clearance with your contact no.waiting time is 2 to 3 months.
I chose the second option and waiting for 3 months now from Saudi Embassy for my police clearance. hope I did the right thing.Goodluck to you.