The place that could be used for translocation would be Cat Tien National Park in Vietnam. Although there are great risks in the translocation to Vietnam and the protection they would be given at Cat Tien, I believe that with the latest Vietnamese restrictions on wildlife trade, the chances of being poached would somewhat decrease. Also, with the addition of more Rangers and possibly a team just dedicated to the Javan Rhinos at Cat Tien, they could have a second stable population.
Javan Rhinos could be extinct in a flicker because of the natural disasters risks at Ujung Kulon. So, a second population would be essential and wise to have, just to minimize the chances of them going extinct and partially having a backup population.