When you say "sprayer" I assume you meant for stream/fan spray. I purchased the Ryobi 4-gallon battery powered sprayer and I LOVE it. It means I'm not constantly pumping that handle (which, for me, would occasionally fall off). I've sprayed 8 gallons on one charge and barely put a dent in the included battery. Unless you have HOURS of spraying to do, it will probably do the job.I've had a Husqvarna backpack sprayer for several years that has served me well until I recently needed parts for it.
Figured I'd go ahead and bite the bullet and get a decent one.
So what's recommended for a manual 4 gallon sprayer? Looking for comfort, no leak, and ease of obtaining parts.
However, if you mean a FOGGER sprayer, then Stihl may be the way to go.