Normally, lack of patience is a signal of a lazy mind - wanting something right now shows an unwillingness to spend time entertaining your brain with your own thoughts.
Changing what types of electronic entertainment (including TV) and toys he has access will probably do the trick.
You see, from my experience, the worst thing TV, cellphones in video-games in general do to your kid has nothing to do with violence or smarts. With the exception of a few games, most of electronic content offers a quick endorphin "fix" in the form of some sort of major success in a very small time frame. This kinda conditions the kid to expect rewards with very little real effort, which causes the general lack of patience of the younger generations.
Fortunately, you can fix this without removing his access to computers, cellphones and the sort, just by changing what games he can play. Games like Minecraft, Terraria, Starbound, Besiege and other building/exploration oriented sandboxes are extremely good for kids and adults alike - getting anywhere in those games demands time, patience, effort and a little bit of research. Stardew Valley is another awesome option. Those games force your kid to think around a problem to find a solution, instead of brute-forcing their way to the answer.
Another thing you can do, if you kid doesn't spend some significative amount of time with electronic devices, is to introduce sandboxy toys - LEGO and the like - or soft puzzles - like sudoku. Those toys and puzzles induce a bit more of thinking than most other forms of play, promoting a more patient demeanor.
You can also let your kid play with you or your significant other, if available, with regular tools or kitchen implements. Building a shed or a model boat with your kid, or even just baking a cake together, are also excellent ways to promote the idea that some stuff just takes a while to finish, and you can't really pay crystals in real life to speed up things - a common motif on a lot of trashy games nowadays.
Some games can be way more mind-intensive than they appear at first glance. Games like Fallout 3 are incredible to play together with your kid. They have a deep story, with a lot of darker, reflexive themes which you can use to promote and model good behavior. Put your kid on your lap, let it play, and talk to him or her about what is happening and how he feels while playing those games. You'll be surprised of what your little guy may have to say.
If you want to stay away from videogames, you have other options. Go to the yard and play with your kid something that needs a bit of patience: fly a kite, read a book together, draw stuff - making homemade comic books is an excellent exercise - plant a tree, or just go to a walk and chat with each other. Anything that wastes time and doesn't have a direct, immediate "success" fosters patience.
Keep in mind, however, that if you want your kid to have patience, you'll have to model patience yourself. If you are always running from place to place, hurried to do your grown up stuff and never relaxing, never stopping to kill some time, your kid will never learn that spending time with not-winning is okay.