I made a mistake and ordered the wrong front sprocket, i ordered 43 tooth and my bike as a 39.

My bike as a rear cassette with 14 tooth, would like to install 16 tooth,

can it be done and where can i get a 16 tooth cassette sprocket

thanks

What type of hub do you have? In most cases you should be able to swap out the cog no problem, unless you are running something rare that no longer has parts available, or if the manuf doesn't offer a cog that size.