A thin wire probe inserted near the electron beam in an electron beam ion trap provides a source of ions for the trap. The wire can be plated with a small amount of source material permitting the use of rare or expensive materials. Here we present results on tests with probes of various materials to demonstrate the success of the technique. In one case a sample of approximately 100 ng of 233U was plated on a platinum wire tip and used to continuously fill the trap for 10 days.