'trace the source' is correct and usable in written English.
You can use it when discussing an investigation, as in, "We need to trace the source of the problem".
He would trace the source of a spring on his OS map or follow animal tracks.
Lyon decided, once again, to trace the source of the attack.
Officials were still trying to trace the source of the attack.
Customers at Tesco, one of Europe's largest retailers, can trace the source of products like watercress.
We can trace the source of infection for all but one of the individuals.
Pairing those data with the toxicity of the sediment, she can trace the source of pollution.
It is easy enough to trace the source of the discontent.
The FSA are trying to trace the source of the eggs used in the product.
Dr. Gerberding expressed hope that the medical sleuths would be able to trace the source of infection quickly.
He said the HSE had warned at the time that it could prove impossible to trace the source.
Noticing that "Shadow Bear" sounded strangely didactic in places, she used Google to trace the source of the writing.
