Diggers brand shellite is a good non polar solvent, the trick is to warm it up as Glaukus said. You could use xylene and the yield would be larger containing more active alkaloids but this tends to create a much darker spice and a bit more mess.
You can buy the rapid tests used at my local community drug & alcohol service online, although they’re a bit expensive at $25 a piece for a urine test. That said it detects all the usual suspects from THC to benzo’s & opioids etc with really good accuracy providing a weak or strong positive within minutes. Just google “DrugCheck NxStep Onsite Test” and you will find them, not sure if this is what you’re after but they work goodluck!