Today's archery equipment has become so advanced that just about any setup will get the job done on an Alaska caribou bowhunt. The state requires a minimum of 40 pounds draw weight and a broadhead that has a cutting diameter of at least 7/8 inch.
Flat-shooting, short axel-to-axel bows work great whether on the open tundra or stalking one of the many willow-choked rivers. Being able to shoot longer distances are a must. Tough-built bows that are forgiving and fit you well will be a big plus.
There are hundreds to choose from, but remember not all are created equal. Caribou are not particularly tough to kill, but you will need good penetration. Choose a head that flies like a field point and does well in the wind.
I take a dozen. They, too, must be durable and fly well out of your setup.
Take two releases, the best binoculars you can afford, and a reliable rangefinder. Spotting scopes are good, but not necessary. Also if you can find room, bring a soft bow case to put it all in. Bush planes are small and big cases get left at the airport, but a soft case will protect your gear somewhat when it's shoved into the Super Cub.
There is nothing like putting on a dry pair of socks at the end of a hard day of hunting. I recommend wool or synthetic with a lot of cushion for your feet.
Rain is a fact of life during Alaska's fall seasons. Personally I like to have a fire at the end of each day. After gathering firewood (as much as possible), cover it with a tarp to keep it dry.
Keeping dry and comfortable is the key to an enjoyable hunt. The long days in September will allow you to hunt 14 to 15 hours a day, and rain is pretty much a guarantee. Personally I use the Sitka line, but Cabela's Dry-Plus is also a good choice.
Bulky, heavy waders are not required for chasing caribou, as caribou are usually found on the tundra. Most times a good pair of knee-high rubber boots that have great soles and good insulation will work fine. I personally wear a boot that has 2,000 grams of insulation and tremendous ankle support.
Not all game bags are equal. Quality bags will not only save you a lot of time, but keep your meat in better shape and your transporter in a better mood.
Last, but certainly not least, rent or buy a satellite phone. They can and will save your life, especially if something goes wrong and you're hundreds of miles from help.