Most of us use a lighted 30X hand-held mini-scope. The strong lens, 30X, means a real short focal length. A short focal length means you should be able to have a built-in light source. You can find them on eBay with a search for "30X scope" for $10 or so.
The tricky part of using a mini-scope is keeping the objective, usually a small sugar leaf, in focus. Here's the trick -- Put the sugar leaf on the back of your hand. You want to look at the underside of the leaf, eh? Then balance one side of the 'scope next to the leaf. You should be able to get and stay in focus by just tilting the 'scope back and forth until you have it right.
Good luck, BigSteve.
PS -- I know this is the new guy section so I gave the answer appropriate for a newby. After a while you will be able to judge the tri coloration/maturity by first noticing the color of the pistils and eventually just by squeezing a main bud. But, learn to do it the right way instead of looking for shortcuts. You'll learn a lot quicker that way.