I am not sure where they buy them, but I think they are a type of telephone wire. There are different colors and patterns of colors on the wires. Cut in short lengths of perhaps, they are threaded around the base of the flower that has been pollenated, and lightly twisted, to mark what pollen was used. The people I know that use wires will designate a certain wire pattern/color to use for a certain pollen for the entire year.
For example, a bright orange wire with pink and green tiny stripe might designate pollen from J.T.Davis, but a red wire with a white wide stripe might be for Ruby Spider.
The wires stay on the scapes really well, and when you get used to using them, I understand that they are fast to put on.
I am "old fashioned" and have always used little white paper tags to write my crosses on, then thread the strings from the tags around the bottom of the flower, and the tag hangs below the flower. The downside of the tags is that some insects will eat the ink off, or if you don't get it on heavy enough it will fade. Sometimes the tags get wet from rain or dew and tear where the tags attach to the string and will come off.
A few years back, the remnants of a hurricane hit Ohio. The winds were so strong and sustained that many people's tags just ripped right off the strings and who knows where they went. The people who used the wires were laughing all the way to the seed bank - because all their wires were still there and they knew what all their pods were, while those who used tags had lots of pods with strings on them, but no tags telling what the crosses were.
An advantage to the wires is that they almost disappear under the flowers for photos and such - and the paper tags are quite distracting. So if you don't want white paper tags in your photos, the wires are a nice idea.
I do believe the wires can be used year after year. The paper tags can be used more than one year, but many people use new ones each year.
