I just made a trainer that I really like:
1) Find a shovel handle. I'm not talking about something like a broom handle, I'm talking about a good, old fashioned spade handle, the kind that is kind of thick on both ends and thin towards the middle. Cut about 18-22 inches of this out with a wood saw, so you have a stout, thick handle.
2) Buy a screw in hook. These can be found in a home improvement store for a few bucks. They are about five inches long, the last two inches are a wood screw, and the rest is a hook covered in plastic. People usualy get them in packs of two and hang bikes on the walls of their garages with them. They are designed to hold lots of weights and stick securely into the wall beams.
3) screw the hook into your handle., so that the screw part is perpendicular too the handle and the open part of the hook faces up. If you try to use some cheap, ramin-wood dowel from the craft store, it will split, so it's important to have the shovel handle. Screw it into the handle until the open part of the hook.
4) You now have a handle with a hook sticking out of it sideways, so that the main cutting edge of the tomahawk is the curve of the hook, and the bottom of the head is the closed side of the hook. These are the two surfaces that will contact a target in striking and hooking, so pad the heck out of them. Any type of foam or sponge works, squeeze it down and tape it as close as possible. Keep in mind that this is going to hit your heavy bag, training partner, and other things. Pad it ten times as much as you think you need too. Pull the tape tight so you can put on lots of layers. You end up with a dense but soft cushion.
5) On the other side of the same end of the handle (where the spike or hammer pol would be on a real hawk) You get to balence it out. Find some tire weights, the small strip kind with the adhesive backing that let you break off one little 1/2 inch square at a time. Get the strip the right length to match the balance of your hawk, and stick it on.
6) Now, wrap the whole thing is duct tape, so it looks like one continuous, duct tape head at the top of the handle. Wrap this all in athletic tape.
I like this trainer. It's a little harder then I'd like, but that all depends on how much foam you use. It feel perfect in terms of weight too.