Okay, going to try to keep this as simple as possible. I don't know what kind of tools you have, what your budget is, experience, etc. So please don't misunderstand and assume I'm talking down to you.
For Kabuto, there's a couple of cheap methods you could do. Easiest one would have to be, hands down…wooden ship steering wheel. Something like this.. Cut out the small, inner circle, which should then free up the actual pegs in the wood. Save them! Kabuto has 5 pegs, and the ship wheel has 6. Use all 6, just in case you mess up. Next, you want to cut out one section of the wheel itself. Try to orient the holes where the pegs used to be in the wheel like an asterisk:
See the top half of the asterisk? What you want to do is cut halfway between two holes to get a C-shape. So cut between the upper left and center, and the upper right and center. You should only be missing the top hole. The top part of Kabuto should now be shaped like a C and have 5 holes.
Remember those 6 pegs you have? We're going to use those for the pegs in Kabuto. First, you want to cut them in half. You want to use the outer section of the pegs (the portion that was originally pointed outward, not the ones connected to the inner circle). Try to cut them in half to be about as equal length as possible. You want the keep a good portion of the square part in order to have it plug into the hole. Don't connect it to the C-shaped portion of the wheel just yet. You still need to prep the pegs for holes.
Hopefully you have access to a power drill or dremel. It'll make this much easier. Drill a hole that's big enough for whatever you're going to use for the Kabuto-strings (not all conventions allow for something functional, so you might have to use rope; otherwise, use elastic latex tubing). Once those are done, you now have to drill one more hole. Whichever will be your center peg, drill a hole VERTICALLY from the bottom of the base going up to the peg. Don't drill too far. This hole will allow you to attach the handle to the top portion of Kabuto.
With all the holes drilled, you can now place the pegs into the square holes for the top portion. All that's left is for you to attach the handle. For this, you'll want a long, wooden dowel cut appropriately for your height and the height of completed Kabuto. Drill a hole at the top of the dowel vertically right into it. To attach it, you'll need what's known as a dowel screw. It's basically a screw that is pointy at both ends, so you can screw two things flush into each other. Hopefully, you drilled the holes straight, and Kabuto is aligned. With that, you're almost done. Just gotta paint it, wrap the bandage tape around the handle, string it, and make an ammo pouch, which I'll leave to you.
Other things you can do differently than what I did: try to sand down the edge of the steering wheel. The top portion of Kabuto should be all rounded. The steering wheel is pretty squareish, so you can fix that, or leave it as is. Also, don't forget to coat Kabuto with a sealant after you paint it, otherwise the paint will chip after a few uses.
Right now, I'm working on a version of Kabuto using PVC pipe as the top portion, which you can see in my thread. It isn't done because I'm busy with Fanime cosplay. Another alternative would be to actually custom cut wood to be that C-shape, although that could be pricey, and you're stuck with cutting/drilling the holes yourself to attach the pegs. Then there's rounding the edges off, making the pegs flush somehow, hiding the screws, etc. Just trying to get everything straight is already a pain. The last alternative, and probably most expensive, would be to have some metalworker weld you one. But it would be really heavy. And while I like using Wonderflex, I don't think it's the right substance to make the top portion of Kabuto. And you'd still need a frame/base, which brings me back to the other above methods.
So this post is already getting pretty big. I'll post some Sogeking mask tips later. Back to the workshop I go! Hope this helps, and isn't too daunting for you.