If the only thing you want to do is upload small images to the web, you could get away with any scanner that has a light source large enough to cover you films.
Images for the web (depending on the size you want) will be in the 72 to 150 ppi range for 4x5, so lot of scanners would do a decent job at this size. You can put up larger files, but most any browser is going to compress them to fit on screen, so you may not be gaining anything. At any rate under 1000ppi for just about anything you are going to put on the web for film as large as 4x5.