where and how can i get exp lock and leftovers? if i buy it from another player, how much will it cost?

Exp. Lock 50 Coins & $500,000,000 + 5,000,000 Clan Credits this you can get from your town/dark alley

Leftovers - you need to use the item finder or dowsing machine and search the maps and collect 50 rubies and 50 sapphires then go to the laboratory and hand then in and there's a 50% chance you will get the item leftovers,if it fails you lose the rubiessapphires and you have to find them again and re do it.