How far north are you located?

HU

If a 5 gal. bucket will work it is about as cheap as you can get. I have mineral tubs, but only because I was able to get them for $1.00 ea.. Mineral tubs and 5 gal buckets stack within themselves, and they stay put pretty well.

If you are wanting something that will go down over a 4 or 6 foot cage, there is going to be a pretty high cost for the material. If I were going to try to build something like that, I might want to make a ring, something like a hula hoop that would sit on top of the cage. Then use another hula hoop ring for the bottom, then attach the material of your choice to the rings. If you thought that you could get by with a trash can liner, they can be bought pretty cheap. I use 3 sizes of trash can liner that I buy in bulk from Morgan supply in Ft. Smith, but I am sure you can get them anywhere. The last ones I fought I think cost from .03 to .10 each. The smaller ones come packaged in 1000 count , the next size that I use is 250 count. I dont remember what the 55 gal size pack is, but I am sure it would be 100 or more. I dont buy these often because buying that many it takes a while to use them.,

I like the way you have the shrink wrap around the cages, mater of fact that is why I have the 55 gal trash can liners, but I had more trouble with fungal disease, even with tearing a large hole in the bottom of the liner. The way I use most of the large liner now is just to cut them into a flat piece of plastic. I drive some wood stakes into the ground to hold the plastic up about 3 or 4 inches and cover the edges with soil, sorts like a small greenhouse.

The kids sometimes use them when they are moving and don't want to get the stuff in the back of the pickup wet.

HU -- I'm in OKC

I would use row cover in low tunnels, but sliding something over a 3 foot tomato cage would be easier. Wind has always been my concern in using Agribon. My garden is small enough that it would not be a big expense.

Problem with wire tomato cage would be tearing of the fabric. Those have a lot of sharp edges to catch the Agribon. I thought about cutting up an old garden hose, slit it open so it would fit around the top edge of the cage.

My cages now are about 6 foot. I have thought about cutting them in half and then as the plant grows, adding a section on top using zip ties.

I cover up caged tomatoes with an agricultural fabric made by DeWitt called Ultimate that gives 10 degrees of freeze protection although I also have some of the Supreme that gives 8 degrees of freeze protection. I bought them online from a company called Agricultural Solutions. Both weights of the DeWitt row covers are dense and thick and do not tear easily like Agribon and Reemay tend to do. My DeWitt freeze blanket/row cover is about 10 years old and has held up really well. I did cut my tomato cages in half many years ago so I could cover them up easily in the spring when freezing temperatures or frost threaten. Once the necessity of using row covers has ended, I just use zip ties to stack/attach a second short cage on top of the first, instantly turning the 3' cage into a 6' cage. In a good year when the tomatoes are growing well, I'll stack/zip tie a third cage to give me a final cage 9' tall. The only drawback to that is that if the plant makes it to the top and forms fruit, I am too short (5.3") to easily reach the fruit at the top of the cage. A small stepladder solves that problem.

https://www.gardeners.com/buy/pop-up-tomato-protector-for-cold-weather/8595060.html?SC=XNET0272#q=Frost%2Bprotection&simplesearch=submit&start=16

And

https://www.gardeners.com/buy/pop-up-tomato-plant-protector-accelerator/8589749.html?SC=XNET0272#q=frost%2Bprotection&simplesearch=submit&start=34

If you search on frost protection on Gardener's Supply, there are a number of things that might work. To me they are too expensive.

That pop up accelerator is pretty much what I had in mind. And you're right, its a bit too expensive