I have trained in Judo and Karate for a lot of years. I have studied kata bunkai for a long time. I'm now moving into Karate weapons training and would like to start with Tonfa. I don't have time in the Karate lesson to start learning something new. The class can't run around me; the students come first. I have looked at Tonfa Kata on YouTube, but don't know if they are made up or not. I would like to learn an original Tonfa Kata if anyone would know one.
I strongly recommend learning weapons in person. It's hard to learn anything over video alone.
If your karate instructor doesn't teach weapons, then find someone in your area who does. And you might want to expand your choices beyond that of typical weapons found in karate schools. For example, you might consider Kali/escrima or Silat.
Another thing to consider is the fact that karate does not officially teach weapons. At least that's how most karate schools are (both Japanese and Okinawan karate). If they are taught, they are part of that particular school's syllabus, but not part of the larger ryu/federation's syllabus, usually. It's usually only taught at a karate school if the instructor went out and learned the weapons on his/her own and teaches them along with karate.
As such, there is little, if any, standardization. The weapon kata that one karate group practices may be different from the kata that another group practices, even within the same style of karate.
In Okinawan karate, the practice of weapons is actually called "kobudo" (roughly translated as "classical/ancient martial arts"). And kobudo is not karate. They are thought of as separate practices, but are often taught together in the same school.
You'll see more weapons training in Okinawan karate schools than you will Japanese karate schools, by the way. It used to be that most Okinawan karate schools taught weapons alongside karate, but that is slowly changing.
In Japanese karate, typically an instructor will learn some Okinawan kobudo weapons and then brings them into his/her own school. It's supplemental training that's not part of the official curriculum of the larger ryu/federation. And it depends entirely on the instructor.
You can often see classical samurai ryu weapons being taught in Japanese karate, also. So this will be sword, staff, spear, and other weapons.
If your style of karate teaches tonfa, or if there are well known instructors within your branch of karate who do, your best bet is to visit one of these teachers and ask him to teach it to you. You can probably learn it over a weekend.
Alternatively, you should consider having a workshop in your school. You would ask someone who teaches tonfa to come and teach a workshop over a weekend. You pay for his air travel, hotel, food, and transportation. If you get enough people to attend the workshop, it will pay for itself. Meanwhile, you can drive him around and get private instruction. If it goes well, then you can invite him back for another workshop every now and then.
If you go with youtube videos, then look at videos that are showing well respected karate instructors. Like I said, the tonfa kata themselves will differ between styles and even within the same style. What matters is that you're training from someone who knows what he's doing, someone well respected. The kata doesn't matter as much as the basic ideas.
Hope that helps.