I made an external, home made smoke generator for my MES. I found that the side wood chip hopper was only good for about 1/2 hr or so before more chips had to be added. I got the idea from a similar smoke generator my brother made for his smoker.
It's made from scrap aluminum tubing, some 3/8" ID vinyl hose, a salvaged aircraft avionics cooling fan, and 2 tin cans. I crimped the open end of a soup can so it fit into the wood chip loading port, and drilled a 1" hole in the bottom of the can. I removed the top of a V8 can, drilled a 1" hole centered, thru both sides of the can, about an inch from the top. I also drilled 6 1/4" holes around the lower edge for air inlets. I also light it thru these holes, using a propane torch. I made a venturi from a length of 1" OD aluminum tube(end of a salvaged tent pole), with 4 1/4" holes drilled in it, at the center of the tube. Inside the 1" tube is a length of 3/8" OD aluminum tube. 1 end of this tube extends beyond the end of the 1" tube, the other end extends to just beyond the 1/4" holes in the larger tube. I also have a small length of 3/8" ID tube as a filler to center the 3/8" OD tube inside the 1" tube. The 3 tubes are soldered together with alumiweld rod. The cooling fan, and venturi pipe are connected with a length of vinyl hose, and the fan is powered by a 12 volt DC power supply I had laying around.
I get about 5-6 hrs of good smoke on a fill of sawdust and wood chips.
I put in about 1/2 can of chainsaw "sawdust", mixed with wood chips, and small chunks, put an aluminum plate on top of the can, turn on the fan, and light the smoker at each of the bottom vent holes with a propane or butane torch.