It comes with a wire frame sports finder. You can use that. If you want an optical finder, this guy on eBay has homemade finders in several focal lengths:
Originally Posted by ChuckP
Most buyers seem happy, a few complain, but he says up front that his $21 plus $11 shipping finders won't match a $200 Voigtlander, nor should the be expected to. They are proportioned for 35mm so won't exactly match the shape of 4x5, and so none of the ones available will match both vertical and horizontal dimensions. Here's a post on LFPF giving the coverage of the 90mm lens on 4x5 and the similar focal lengths for 35mm for comparison:
A 90mm lens for 96x120mm film (4x5 in most holders, some vary by a wee bit) has the following angles of view in degrees: horizontal: 67, vertical: 56, diagonal: 81
A 21mm lens for 24x36mm film has the following angles of view in degrees: horizontal: 81, vertical: 59, diagonal: 91
A 28mm lens for 24x36 gets you, in degrees: h: 65, v: 46, d: 75
Some are opting for 21mm for the closer match to vertically. I felt like that will show more in the viewfinder than I'll get on film horizontally and I'd rather have it show less since I can crop in printing if there's stuff I don't want on the film, so I opted for the 28mm.