Note that I have tried the PEGit method with ok recovery of 57%, but the purity was not good/clean (as expected) sine this is a concentration product only without any purity claim (O/N incubation + 35 min. prep time using total input of 1.5 to 2 x 10E7 ivp). Remainder of lenti (43%) was found in the supernatant that is slated for waste.
Another option to try is Cat. # FTLV00003 Fast-Trap Lentivirus Purification and Concentration Kit from EMD Millipore. It's based on a bind-wash-elute method and has a final buffer exchange using size exclusion centrifugal.