Can you put something to replace your belly button ring if its lost?

Yes there are rings, bent barbells, navel gems (bent barbell with faceted stone in the bottom bead). There are options but you need to make sure you are buying quality jewellery, the junk in the mall is more often than not just that junk, made from inferior metals and sold in little boutiques ( Claire's, Ardene's and the like ) as body jewellery. If you want quality jewellery go to a professional body piercing studio where they take pride in selling quality jewellery made from bio-compatible materials that won't react to your body. Buyer beware if the price is too good to be true chances are it is.