Well I searched coingecko, coinpaprika, coinmarketcap
YoBit - DEM/BTC Trading Pair
BTCPOP - DEM/BTC Trading Pair
Freiexchange - DEM/BTC Trading Pair
these are the exchanges I found still active and doing trading with DEM. Make sure you have current wallet before depositing DEM to these exchanges, use the Exchanges at own Risk as well they have not been tested by me.