Garmin Alpha (tracking and training) and Astro (tracking only) are the best, but expensive. They have a 9 mile straight line range, but not sure how well they work in the mountains. The Alpha is $900 for 1 collar and handheld. You can add additional collars. An Astro with 2 collars probably will run you about the same.
If you are not an upland game hunter and only want it for this one trip, maybe you can call around to several upland hunting guides and see if one would rent you a couple of collars and a transmitter (season is over so they aren't using them and may want a little extra money).
If you want to read about them and other brands, the best place I have found is Gundogsupply.com, big selection and reviews and articles. A really good supplier....also check out their engraved dog collars, high quality and cheap and you can put your phone number, etc on them, wouldn't have my dog without hers.