In my industry we get tested regulary for drugs and alcohol in the UK, when i am going to a site with a known history of urine testing before being inducted onto site, i use one of these 3/4 hours before my induction appiontment.
Zydot euro blend.
They are a "masker" not a system cleaner and cost about £25 per bottle, it's a powder that you mix with 500ml of water.
I have used these 7/8 times in the past decade and passed each urine test.
If i am going to a site that uses saliva tests, i abstain from THC for 36-48 hours
and have passed every saliva test also.
I can only recommend the above product for THC.
Availability outside UK/Europe is unknown.
Hope this helps someone.