Try to find minus the desired composition on one of the free sites backing tracks. One of these sites - You can use the list of domestic and foreign artists in alphabetical order, and enter the name of the song in the search box. Minuss songs in the style of pop to find the easiest way them online majority. For rock music, for example, there are special resources.
There are sites and forums where musicians and vocalists communicate with each other and exchange their backing tracks. One of them is a music forum Sign up and leave a request for the desired minus perhaps some of the users he is. Also use the search - suddenly someone has already posted on the website that you are looking for. A good way of getting new backing tracks - communication with fellow musicians (if you are professionally engaged in the music). Invite a friend to share the available cons. Such mutual assistance can save you time and money and build up his repertoire.
Attempts to find the right backing tracks in the network is not always successful. It happens when the song is still quite new, when it is popular in narrow circles, etc. it Happens also that available cons poor quality or don't have backing vocals. In this case, use the services of a professional arranger. They often offer the creation of quality backing tracks for a fee. As a rule, before you make the order, you can see the finished work of the specialist and make up their minds about their quality.