Have you tried one of these hits: http://www.google.de/search?q=phe+auxotrophic

I'm not sure if there is a pre-existing Phe auxotrophic with the λDE3 phage lysogenised that is commercially available. Your best bet is probably to source a regular Phe auxotrophic strain and then use a lysogenization kit to integrate the λDE3 phage into it. Novagen (Merck) sell a suitable kit, details can be found here: http://bit.ly/aNSEEf . The procedure is relatively straightforward. From that web page:

The λDE3 Lysogenization Kit is designed for site-specific integration of λDE3 prophage into an E. coli host cell chromosome, such that the lysogenized host can be used to express target genes cloned in pET vectors. λDE3 is a recombinant phage carrying the cloned gene for T7 RNA polymerase under lacUV5 control. Lysogens are prepared by co-infection with the three provided phages, and can be verified by plating the T7 Tester Phage (a T7 RNA polymerase deletion mutant). This phage is unable to make a plaque on cells that lack T7 RNA polymerase, but makes normal plaques on λDE3 lysogens in the presence of IPTG.The T7 RNA Polymerase Monoclonal Antibody can be used to verify the presence of T7 RNA polymerase in the host strain by Western blot analysis.