Check out YOUTUBE. If you search on yoga or whatever form of yoga you do, you'll find hundreds of different yoga workouts posted. You could do a short meditation for 5-10 minutes or a whole class for 50-60mins. I've seen segments on just pranayana breathing techniques or power yoga poses.
If you have some prior experience with yoga and know the basics, you might want to check out some yoga DVDs too. Before you buy, go to the libray and check them out first. why buy when you can borrow ? your local library is not only a great resource for books, you can find DVDs and CDs too.
I've been looking for a yoga class myself. Most tend to be either early in the morning before work or in the evening after work. occasionally, you might find a lunch time class. You rarely find classes during the week at 2 to 4pm because most people are working. It's not a popular time. So, if you want to do something on your own, look at some of the workouts posted on youtube. there really is a huge selection.