Outdoor centers like Cabelas and Bass Pro Shops have this type of equipment. It is also available on eBay and Amazon. Radio Shack is a good source for two way radios.
One can purchase VHF two way radios from many places. Examples of such places are Dino Direct, Pirates Cave, DH Gate, Merit Line, and Digital 2 Way Radios.
There are many retailers from where one can purchase two way radios such as Ebay and Argos which offer a wide variety of two way radios at various prices and specifications.
One can purchase a set of Motorola UHF radios at various retailers. One can purchase a set of Motorola UHF radios online at websites such as Two Way Direct and Buy Tow Way.
One can purchase BearCom radios directly from BearCom online at their website. Their website contains over fifty different, high-quality 2-way radios.
There are a number of options for one wishing to purchase long range two way radios. These can be found on sites such as Buy Two Way Radios, Overstock, Amazon and eBay.
You can purchase two way radios from the Argos catalogue store in the United Kingdom or from their official website store. Alternatively if you are in the United States you can purchase from a Best Buy store or from their official website.
Handheld two way radios are also called walkie-talkies. Try the websites "Discount Two-Way Radio", "Fast Radios", or even eBay. You could probably find something good on at least one of these websites.
Handheld UHF radios may be purchased at Two Way Direct. They are also available from Two Way Radio, Powerwerx, Rugged Radios and Uniden as well as PSI Company and Tech Wholesale.
http://en.wikipedia.org/wiki/Two-way_radio
GMRS two-way radios can be purchased from many places. Some of these include Amazon, Best Buy, Target, Costco, Rei, Buytwowayradios, Cabela's and eBay.
There are various options for those interested in purchasing Motorola two way radios. Sites like Walmart, eBay and Amazon have general options. More specific radios can be found at spots like Two Way Direct and Global Industries.
2 way radios are not as popular as they once were but that's no reason not to purchase one for your children if you think they'll enjoy it. Sometimes there's a certain nostalgia associated with older electronics.