You can buy round glasses in Jeffrey's Manhattan Eyeland, Jeffrey D Nightingale Pc or Manhattan Ey etc. But i didn't buy eyeglasses from those shops because i have perfect vision. So, i don't know which store provide cheap round glasses. I find some reviews about Jeffrey's Manhattan Eyeland athttp://www.yelp.com/biz/jeffreys-manhattan-eyeland-new-york, you can have a look. BY the way, if you look for some very cheap round glasses, you can try to order it from online shops which are much cheaper.
You can try The Eye Doctors at 3012 Anderson Ave Manhattan, KS. They offer most discounted inexpensive prescription eyeglasses, prescription sunglasses. Opticians in the stores will help determine your pupillary distance (PD) and fit glasses, sunglasses, contact lenses and other eyewear based on the prescriptions written by optometrists and eye doctors. So you can just go to their real store to choose one that you like and try them on. The staff members may help you to find the most suitable one for you. If you find their round glasses are expensive, you can search them online which may be much cheaper than the real store in Manhattan.