I just use those disposable ziplock/glad containers. Loki's a pro at urine samples as we do one almost monthly. He doesn't care what I stick under him.
I tried with Sam (she has a UTI too) and she was more interested in the container than peeing. She thought I had treats or something. Finally she went and I stuck it under there. You have to get them facing away from you and stick it under once they start going.
(BTW, Sammy had a lot of blood in hers so they did do the cysto once we got to the vet. I don't know if her drugs are working
It's been 3+ days...)