I would recommend just getting a click. They cost under 2 dollars at any pet store. For dogs, the initial intro to the click, called "priming" can take anywhere from 10 minutes to three days. For cats, depending on the cat, I'd say 3 days to two weeks.
Here is what you will do.
You can be standing, and the cat can be on the floor or up on a stool/table so they are at your height. Get a yummy "high-value" treat, something that the cat REALLY wants. If the cat is anxious, meowing, swiping, and all around showing a lot of interest in the food, that is good. Starting on the ground is easiest. Click and drop a treat immediately after. The first day, the cat won't get it. On the second day, wait for the cat to look away and click and drop/give the treat. I would split this up into anywhere from 3 to 10 short session a day, at 15 treats each session. That's a lot of treats so have them be small. Shredded cheese is a popular choice for me, you can give them individual shreds and they never really get too much. (not recommended for sensitive tummies) Eventually you will notice that when the cat looks away, the click will snap their head back to attention looking at you, looking for a treat. At this point, you know they have been "primed" to the clicker.
I have a lot of advice and experience in clicking training cats and would be happy to share some more of my tips with you'd if you like