Cheaper alternative to synthetic urine for a home-drug test

Basically, I got caught. While, I told my parents that its the only drug that has ever worked for my insomnia, depression, and self-harm problems, they still will not let me continue, and after two months, they will start drug testing me weekly. It's become such an important part of my life, and has helped me so much, that stopping is simply not an option.

Now, I really don't want to spend the $30 a week for synthetic urine, expecially considering how often I'd have to buy it. Because of the fact that I'm in my parents house, I have to go to a lot of trouble to get this from the internet.

I've been thinking of using a friends urine, however, this doesn't keep very long, and smells terible if not refrigerated(and I can't put it in my refrigerator) . Again, this isn't a lab test, its a cheap home-drug test. Is there anything I can make? Perhaps synthetic animal urine like this. However, I'm not sure if this is yellow, and if its not I obviously can't use it.

I was also considering using small amounts of powdered urine, then mixing it with water and yellow food coloring. While this obviously wouldn't pass a lab-grade test, it may be an option for a home-drug test.

Anyone have any experience with this? Any help is appreciated greatly.