the nice jazz festival still has tickets for the 22nd july, the tickets are for entry into the whole area within which LC is playing on what is i think the main stage so no seating but get there early and get to the front. if you go to the jazz festival website: http://www.nicejazzfestival.fr
there is a link for buying tickets and a list of approved agents i couldn't get the link to work so googled carrefour which is one of the agents and booked an eticket through them, needed to either speak french or use a page translater like translate.ru, the page for carrefour is http://www.spectacles.carrefour.fr
then search for nice jazz and follow links to buy, i tried for a three day pass which wasn't working so just got a day pass for the 22nd in the end, print out ticket done. YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEES
Cost was 52 euro's minus 1 for using eticket.
Hope that helps good luck