Lots of posts in the DT forum of individuals who have had success subbing with synthetics at LabCorp.

Given the choice between synthetics and dehydrated, the synthetics win hands-down in my book. Dehydrated urine requires mixing, which lends itself to mistakes such as overmixing or undermixing. Once mixed, the dehydrated stuff has to be used pronto. Synthetics such as the QF are premixed and ready to go. Plus, the QF can be stored at room temp throughout its 18-24 month shelf life, and it can be heated and reheated over and over without hurting its efficacy - excellent for "practice drills". Dehydrated urine on the other hand, is pretty much a one-shot deal.