Very nice round of stores and I highly recommend the one on 43/Deerfield- Fish Planet. His tanks are immaculate. I was jut there a month ago for moss.
If you go further north on 41 and Delaney there is a warehouse type store that sells any parts you can think of. Prices are decent and nice ranges of glass diffusers for $15.00. Here's the link:http://www.aquacave.com/CO2-Reactors...users-C34.aspx