Security on tertre rouge is the tightest down there so it will be difficult, however on the first few days things are usually a little less tight so try to get an extra exit pass, usually after few days we will end up ith at least one extra pass for the campsite entry, however the main gate under the bridge at tertre rouge corner will be harder, they use an electronic reader there and the only way to get in is if you have a camping pass for the bike, and a spare TR will be hard to get.