Go to a building site and see if you can get some 6"x6" steel mesh that they use as reinforcement when pouring
concrete slabs. The rolls are 50' or 100' long and 5' wide. This is too heavy to cut with a regular pair of pliers, so you are going to need a light duty bolt cutter. When you lay it out on the ground (and give it a good stomping so it will lay flat), cut yourself a piece that is 5'x5'. On one end, cut close to the wire so that you end up with almost 6" of free wire that you will use to stab into the ground.
Now comes the bending part. You could cut two section off of one edge so that you have a piece that is now 4'x5' and you could bend it to a square tower, but I like towers with 5 sides. Take your piece and bend it into a tower, realizing that you have to make a lot of small bends to get it to come into shape. Sometimes a piece of heavy lumber like a 4"x4" makes a good template to bend against. When you start working on your last bend, that will be closing the side of the tower and now you have to fasten two edges to hold the whole thing together. Heavy duty wire makes a good twist-tie material for this part. Or you can use scrap 6" pieces that you generate during the cutting process. Again, you will need a hefty tool to bend these clips and close them.
Now you
should have a pentagonal tower, 1' on a side, that is 5' tall, with 6" tines on the bottom that you can jab into the ground. These can blow over (last night's storm blew one of mine over, and I had to right it this morning), so you may want to think of some combination of tent pegs or bricks to keep it well anchored.
I grow my tomatoes on towers like these, one plant to a tower, and it seems to work well. Sometimes the tomato will want to shoot out the side and take off, defeating the purpose of the tower and unbalancing it, but judicious pruning will take care of this. Rarely does anything stick up more than a foot above the top of the tower, and again, this can be pruned back.
These towers also work very well for peas. I plant my peas in January and harvest them in April, and just about the time the peas are done for the year, it is time to put out the year's tomatoes.