Check out Home Depot's online selection if you're looking for a brand new smoker, particularly the Masterbuilt line. I've had several different smokers, starting with a Little Chief, then a Bradley pellet, a MB dual fuel propane/charcoal, up to my current MB digital electric. Bradley's are pricey and the cost of pellets can add up but they require relatively little attention when running. Charcoal/propane are cheaper and fun to use because you can scavenge dead alder sticks from the woods to run them but they require lots of attention to maintain temperature/smoke if you run any long smokes. My digital electric is the simplest to use and least expensive, just requiring a chunk or two of wood every hour or so. I'm getting lazy in my old age. I highly recommend the digital electric if you also want to do ribs, brisket, pulled pork, etc. in the future.
However, you said you'd like to cold smoke fish. That's a different beast and requires a smoke generator that doesn't pump out heat, just smoke, so you can smoke fish in your bbq or a cardboard box if you want. Check out Amazon, there are quite a few.