'online sources' is correct and usable in written English.
You can use it to refer to information that you have found on the internet. For example, "I found some interesting statistics in several online sources."
There are also many online sources, such as Etsy, eBay and specialist vintage linen storefronts.
This can be obtained from your local craft or fabric store or through online sources.
The Millions' roundup of the best online sources for fiction.
There are hundreds of online sources of free sound effects.
Newsweeklies, however, are suffering from a defection to online sources.
Increasingly, this service response includes online sources and resources.
Additional online sources to help students improve their writing.
And, of course, we can't forget the online sources.
I usually try several UN online sources and finally GOOGLE.
There are plenty of online sources for sofa legs, like Bing's (bingltd.com) and rockler.com.
They had been incorrectly listed in online sources and in the daily bulletin.
