Currently you can stream the documentary Gideon's Army with a Prime Video subscription. If you already have Prime then you won't need to pay anything extra to stream Gideon's Army. If you don't have Prime Video then try it for free for 30 days, and just cancel if you're not enjoying it!
If you don't have Prime Video then you can buy or rent Gideon's Army to watch online via a number of platforms including VUDU, Google Play Movies, iTunes, Microsoft Store and YouTube. You can rent the documentary for as little as $2.99