BTW, does poultry contain creatine?
Not nearly as much in comparison to red meat. But if youre looking for an alternative to red meat, consider fish.
Other than that, creatine supps are the way to go. Whichever source you choose, be sure to do your creatine loading at least 3 days before the scheduled U/A to allow time for the body to convert creatine into creatinine (the end waste product that is present in urine).

i'm sure they don't have an upper limit.
Thats right. There are no upper limits established for creatinine. As long as the creatinine level is above 20 mg/dL, its satisfactory.

However, this doesnt mean one should go overboard with creatine-loading. Doing so can result in long unwanted bathroom sessions, sitting on the toilet seat.