this is the one i use and it works fine its a cheap micro science kids toy 100x 200x and 450x magnification
To growers like you and I, thats the Rolls Royce of looking at trich development and color
Myself, I use a 30x jewelers loupe most of the time or a a digital camera on a small tripod, I have one of those pocket 60-100x pocket microscopes, more of toy, but it works, but having a desktop simple microscope like you have is the best option, maybe not the easiest, but still one of the best methods, although you'd probably have to take a leaf sample to put on the glass slide.
...But in a pinch, you cold take a pair of binoculars and look at the trichs with the rubber eyepiece towards the plant, at about a quarter inch away, you can see the trichs coloration pretty well.