Oakley boots are awesome. They run about half a size small. They also only last a year or so of wear (every other day). Also, their gloves are the best I've ever used. Their goggles are so-so.
Danners are almost as comfy but a bit more expensive. They last forever(ish) and you can take them / send them in to Danner for repairs if they start to go.
Military boots use military sizes. And there are only two of those: Too big, and too small. With boots, you really need to try them on. Really, really need to try them on. The exact pair you are buying. They vary by both brand and style, and sometimes by the boot within the style in cheaper brands. I have worn everything from an 8 1/2 to a 10 1/2 depending on who makes it and whether it is a summer desert or waterproof winter boot. And buying used boots is a recipe for discomfort. Boots "break in" to the user, and it's pretty much a guarantee that your foot size / shape / pressure spots won't match the last guy.
If you are looking for a Delta skate helmet,
http://www.pthelmets.com/ has them with or without rails and drilled for an NVG mount for a pretty fair price.
Kneepad inserts (ACUs / 5.11 pants) are pretty nice, and pretty cheap. They stay where they need to and don't get in the way. If you are looking for functional, they just rock.
If you need "pretty" instead, take a look at the Blackhawk kneepads. They are padded enough to be comfy. I'm not a kneepads kind of guy, but those hold up. Only problem I ever had with them was that the plastic is a bit wobbly to shoot from. Of course, with airsoft that's no big deal, but still. It's yet another bit of kit that is improved remarkably by adding a chunk of skateboard grip tape.
And on that note, I absolutely recommend skateboard grip tape for anything that you need to hang on to whilst wearing gloves. I wrap the magazine well of AR / M-16 / M-4 platforms with it for better control, add it to the handles of pocket knives with untextured sides, put x's of it across plastic kneepads, and put it basically anywhere I want to have more traction, friction, or grip. It's almost as useful as 550 cord.