Hi
Superfeet or Soles are probably what you are after. Really, just like boots, it's about finding the one that fits your needs--and your foot-- the best. Both are quality products and have a lot of fans.
In the case of either, I would strongly recommend going to a store that has both, and has some trained sales people that will allow you to try them on and find the fit that's right for you. A good quality outdoor equipment store would likely be a good choice if you have one in your area. I have neutral feet as well, but this summer I was training for a Grand Canyon hike, and started to get Plantar Fasciitis. I replaced the insoles in my boots with upgraded insoles, and the issue went away.
After trying both Super Feet and Soles, I wound up with the Soles Dean Karnazes. You might look specifically at the Ed Viesture model, they are made for high volume footwear, and made my Salomon Quests a bit too tight. The Soles allow you to heat them in your oven and then put them in your boots for more of a custom fit. It might not be completely custom, but it does help with break in time. I have a friend who does serious endurance races--Ironman, Leadville, Etc, and he swears by Super Feet.
In the case of both Super Feet and Soles, I had to go up at least one whole size for the insoles and then trim them at the toe. This is not at all uncommon. The key measurement is the length between the ball of your foot, your arch and your heel--not the overall length of the foot. That's why it's so important to try them on. Every foot is different, and every boot is different. Take the boots you are going to put them in to also check the fit-especially if you want them to take up some volume.
Full Custom orthotics are an option, but they can run you several hundred dollars. If you're not having pronation problems, I don't think you need to go that route for now.
Hope you find one that works for you.