You should be able to find a tracer that threads on like a silencer. Tracer ammo is pricey though and for the most part in the day time with white BB's you can see them anyways.
If you want to do a tracer effect during the day time do this.
Get a bag of black BBs
Get a bag of white BBs
Pepper 20/80 white to black.
You now have a tracer mix.