I think you could use the rebar or some long wooden stakes. I don't know if I would try to add another cage on top, you could probably just tie the large stems to your stakes and grow them like staked plants. The stakes will have to go pretty deep into the ground to do any good.

I don't know how you could anchor them to the beds, it will be the top that is heavy and falling over--I don't see how that would work?

Another option would be installing a large cage over the small one you already have, but getting to your tomatoes would be a pain for the lower branches.

Or, you could just let them grow out and sprawl. It would make them more vulnerable to pests on the ground, but as long as you put plenty of soft mulch (like straw) underneath them to keep the leaves from getting dirty, it would probably do ok.

If it were me I would get two 6 to 8 foot T-posts and put them on the inside of the cage. As the plant grows taller than the cage you can tie twine between the two posts on either side of the tomato stems to keep them growing vertically. The posts will keep the cage upright and prevent it from blowing down.

Aw, Greg beat me to it, posting in the time it took me to log in! ;) except if your other tomatoes are in a line with this one, I would put the posts at either end of the row and run twine through on a few levels, which could keep the bottoms stable. Then as the plants grow higher you could do a Fl. weave above the tops of the cages. 6 ft posts would work too, but by the time you got them in they would only be 5 ft or less tall.

I agree with Julie717

I am planning to buy rebar from Home Depot. they have 22 feet length in 3/8" diameter for $6 or so. I can easily get three 7' sections out of it. 12" goes into the ground and 6' is how high I want my support stakes. THen I plan on making florida weive usig jute twine. Last year I used 1/2 x 4 stakes that were 5' long, did ok but I wish I have couple more feet of support at top.

You can add 3 guide wires to it, hammer 3 stakes in the ground about 2-3 feet away and attach 3 wires.
Add another cage to the top, wire the two together and add the guide wires.

I have some of those baby cages & I use bamboo canes, 12-18 inches in the ground around the cage. The canes are 6-8 feet above ground.
I think I will make wire cages, for next years crop.

sunnibel, I am using the Florida Weave for the first time this year, one of my many experiments. The plants just got their first tying in today.