UCO makes candle lanterns, but the last time I bought some candles for one, REI said they were being discontinued. Suggest you get the mini lantern that takes tub candles. You can stock up on those at a dollar store or Walmart. Most places are switching to liquid candles or l.e.d. lanterns. That stinks because I use a candle lantern to keep my tent warm when camping. L.e.d.s don’t work for that.
Maybe REI was mistaken? Nothing on UCO's website or on any social media. That item is their bread-and-butter, "since 1970" so I can't see them folding it up. You can get a 20-pack of their citronella candles for $30 at that Brazilian river online shopping site. Everything candle-related at their website is currently "in stock".
Maybe they meant that REI is discontinuing carrying UCO? A lot of outdoor industries have found they get more profit through direct sales than selling through brick-and-mortars - or REI hasn't found selling their line to be continuously profitable. There isn't much to fail requiring upgrades or replacements.