Your best bet is going to be picking up some cheap thc strips off ebay. I pay about $1.25 each.
Subbing is still an option with synthetic urine. I bumped a trailer once and had to go for a UA. I just keep the synthetic urine and heat pad in my pocket. As soon as it happened I knew they were going to test me so I just activated the heat pad and moved both to my crotch. Stall for about a half hour and temp was at 96