The creatinine test strips can be found by doing a search for drug adulteration test kits on google.com. Prices vary depending on the vendor, but they are dirt cheap overall.

TIP: When I use the strips, particularly when I test premixed synthetic urines such as the Quick Fix, I prefer not to submerge the strip in the sample. For starters, too much care must be taken when you withdraw the strip from the sample to take a reading. When the test strip is withdrawn vertically, you stand the great chance of cross-contaminating the other panels when the colors of the reagent pads "bleed off" and run down to the neighboring reagent
pad(s), making for erroneous readings. Therefore, the test strip would have to be withdrawn from the sample as horizontally as possible without spilling any of the sample. A virtually impossible feat.

Second, by dipping the test strip into the QF, the chances of reagent contamination of the QF solution itself are higher than you think. Remember, youre planning to use the QF once it passes your validity checks, as opposed to a real human sample that eventually gets discarded by the lab once the validity and actual drug checks are completed.

Perhaps to overcome all of these headaches, I instead use a dropper to withdraw the sample from the container (like the labs do) and, with the test strip laying flat on a paper towel, I make drops on each reagent pad (panel). When doing this, make the drops thick enough to create a bead on the pad. Then, after a minute, drain off the excess by tipping the test strip on its side, before getting a reading. Again, the idea is to prevent reagent pad cross-contamination, as Ive described earlier.