With 5 cats I have found it necessary to take urine samples, and do my own urinalysis at home. I try to do the younger animals twice a year, and the older ones 3 to 4 times year unless there's an issue and then I do it immediately. I use 2 different methods of collection. The situation at hand dictates the method of collection. If I'm taking a sample just for a checkup I will use a spoon (gravy spoon shape) which holds about 20 mL, and the volume is sufficient for what I need. What I do is wait until the cat is going to the litter box, and then place the spoon under the cat's bottom, and in the stream to take the sample. This works great with some cats no problem. Some have their butt too close to the litter, and a very light lift on the tail can help. This does not work very well on a Manx, and the Pixie Bob is not impressed. I have one that will not agree with this idea at all, and if he could speak I think he would tell me where he would like to see the spoon placed, and that wouldn't be under his tail.
The 2nd method I use is a clean litter box that I put some clean natural aquarium gravel in. I will then put the litter box, and the cat that I want the sample from in a separate room by itself. Then start the waiting and checking game until you receive the sample. After the sample is deposited in the litter box I will tip the box so that the sample runs into a corner, and I will use a syringe to receive the sample and put in a container. I will then wash the gravel, and put it out in the sun to dry for a couple of days, before bagging it again for the next use.
Here are a couple of websites that are worth the read, and give you some idea on taking the sample, and the testing procedures of the urine sample.
I have one small issue with the author's timeline of 24 hours for freshness. Lab techs tell me that it is best to have the samples tested as soon as possible after they have been taken. Unrefrigerated they should be done within 2 hours, refrigerated 4 hours after that the accuracy will start to drop off. Just something to check out.
Hopefully this will help a wee bit, and your kitty will be accommodating and give freely of itself in your endeavors for retrieving a urine sample.