If you want to get cheap pinhole glasses, you can just search it in eyeglasses shop that nearby you. Or, you can also search it online. I believe you can affordable pinhole glasses online. I just search it online and find there is a sites http://www.pinholeglasses.org/ where have many information about such glasses. Hope this will help you find pinhole glasses at a cheap prices.
If you have enough spare time, you'd better go to the eyeglasses shop to have a try. Only after you try it on can you find the most suitable one. If you just want is to have a cheap one in an easy way, the better way to search it is to go online. Here I will recommend a good online shop for you http://www.pinholeglasses.org/. The price there is good and the designs are various. It is worthy to go and have a look. Hope you find your pinhole glasses.
Pinhole glasses which are well known as stenopeic glasses are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens. Because of being combined with certain eye exercises, they could help you correct vision. In other words, pinhole glasses are really useful for nearsighted people and farsighted people. if you want to get some cheap pinhole glasses, I can give some messages which may help you. You can go to the http://www.dhgate.com/fashion-sunglasses-pinhole-glasses-eyesight/p-ff808081359ee1b50135a8f102b73793.html. And I can find some useful ones, at the same time. The price is also ok. But you should pay attention to the quality too. And know something more about what should be careful when using it. This is also important.
Of course, it will do harm to your eyes. In my opinion, you should take off your contact lenses. Even if you wear the more permeable silicone hydrogel lenses, sleeping in contact lenses is never a good idea. It can lead to eye strain, infections and dry eye syndrome. Wearing contact lenses over a long period of time, especially if you habitually sleep in them, can also lead to decreased corneal sensation, which results in decreased tear production. It can also make your eyes feel tired and strained the next day morning. Sleeping in contact lenses can lead an increased risk of conjunctivitis, also known as pink eye. This condition can be caused by an infection. Long-term contact lens use can lead to dry eye syndrome. Wearing contacts overnight can speed up this process. Sometimes there are just some situations which may make you so tired that you don't want to take them off. In this situation, wear glasses instead for at least the next day. This will be a good advice. And also you can do other thing to avoid dry eyes.