You can find a website list for do this in the page: Track drawing websites
Openrunner is the best one for me and the most important: this website automatically add the elevation data needed to create the profile.
You can find on this site a quantity of already registered tracks.
You can also try the tools on www.mygpsfiles.com, easier to use.
You can also search gpx tracks on https://hiking.waymarkedtrails.org (Be careful, they do not necessarily have the elevation data needed to create the profile).