Well, Academy has mini-logs in large onion sacks. It's about 12 bucks a bag. The bags are 1.5 cu. ft if I remember correctly. They work in a pinch, or if you don't have room to store a cord of wood. It's what I use in both of my smokers. Some of the mini-logs are about 8-12 inches long and up to 4-6 inches in diameter. They work good for me. Don't let this picture fool you, that is a massive firebox and there is nothing really there to show the proper scale.
Well, it depends on your smoker and your temps. In my little smoker I can use a single bag for multiple burns, but in my big smoker I can use a bag or 2 per day, but a day of smoking for me may last 18 hours. The big smoker, the one in the pic has a 30inch diameter x 7ft long smoke chamber made of 1/4 inch steel and 28 inch diameter x 28 inch long firebox made of 1/2 inch steel. It takes alot of heat to get that one up to temp and hold it there. If you have just an average size smoker, go buy a bag of charcoal and a bag of mini-logs, use the charcoal for heat and throw one log at a time on the fire for smoke.