There are several. They're either 45º or 90º so first decide on that. It really depends on your application. I find the 90º a little awkward for everyday use; the 45º is a better compromise IMO.
Then they come in metered and non-metered versions. If you like to use a handheld meter, then it's a no-brainer. The non-metered are also lighter and cheaper. Those that are metered come in several varieties, from the older type that give you an EV value (e.g. PM51) or the newer type that give you typical shutter/aperture values (e.g. PME45, PME90). The latest PME finders truly are NICE. But they're pricey.
Then you have a variety of older prisms that don't have any metering and are decidedly "old school" but work just as well as the newer types. You can also use Kiev finders, which also come in a variety of flavors. Compatibility and quality are, "less than par" generally. 😉
One thing to keep in mind is that the WLF has the highest "out of the box" magnification for critical focus. You could attach a flip-up magnifier to a prism which should give you a little more, but you're building a real monstrosity here...