http://www.digikey.ca/ is a great website to buy electronic components .
Usually we can check or find the parts we need on Digi.Key.
This website can tell you whether they have the items or not.
Sometimes, if the electronic components are out of time, they will be very hard to be found. As a result, you can search phrase like ” the alternation of ….” on google or other website, in order to find the available components.