Fifteen years ago, nobody had ever seen a fancy stainless steel radial plate with dozens of holes and bolts.
I was going to make something, not buy. Didn't seem too tough to drill holes, even if they aren't even and perfect.
As mentioned, aluminum would be better. Copper plumbers tape is ready made with holes!
Soldering or clamping to a larger piece of copper wire is fine.
Those fancy plates are a convenience, nothing more. They don't improve performance a wit. No need to spend +$100.
Radio Shack has an aluminum project box for about $4. I drilled holes and added screws and some wing nuts to use it as my attach point for the radials on a portable antenna.
Good ideas, all. I forgot about the RS boxes. I think I have a few laying around somewhere.
Just to update, yesterday afternoon I tried out the antenna with electrical box in the park. Same results, able to hear OK, but the tuner had a hard time tuning this time (but it did find a match) and didn't get out at all. I then took all the radials and put them all on the same screw as the ground wire and the very next attempt I was picked up by a station in Texas. Background noise came up, along with more signals on the waterfall than I'd seen in a while.
The take-away for me is that junction boxes don't work, don't bother with them. At least I'm only out about $3.50.