What we had to do was use a litter tray with some special litter in it
(small clear crystals, I belive its called lab litter).  When cat had done
his bit we used a pipette (supplied by the vet) to take the sample from the
tray and placed it in a sealable tube (again supplied by the vet).

Obviously if you have more than one cat keep the tray away from the other
cats!

My method has worked with all of my cats except one who is especially
stubborn and pig headed.  I found that they are creatures of habit. Put
them in the kitty litter and they will pee. so, beforehand, I get a
clean and sterile bottle ready. I also prepare a shallow bowl. when
kitty starts to go I slip it under their rears and collect the urine.
You might have to put them in 2 or 3 times for them go get the idea
but, as I said, this has worked well for me except for thick headed,
but adorable, McDuffy.

I use a medicine dropper.  If you don't have one you can probably buy one at
a drug store.  I put plastic from a dry cleaner or saran wrap across the
litter.  The cat goes in, makes on the plastic, and I just get it into the
medicine dropper.

--
Barb
Of course I don't look busy,
I did it right the first time.

If possible, confine kitty to a room and use packing peanuts in litter pan
(the styrofoam kind not the biodegradable kind).  If that doesnt work, use
aquarium gravel sparingly.  You should be able to drain enough to get a
pure sample.  Rots-a-ruck