Other than Leedy, the only other place I've seen 10/24 tension rods is on some inexpensive (cheap) student / toy single tension snare drums. They're long, but can easily be cut down. I may have one if you run into a jam (I see you're in Japan).

The easiest thing would be to go to a good hardware store and get a 10/24 bolt...either one with a fillister head or allen key head.

All modern drums use a 12X24 thread lug. In the past, Barry, Duplex, Leedy and Conn drums used 10X24 threads. The Leedys had slotted heads. The Duplexes had square heads. The Barrys and Conns had six sided heads. 10X24 lugs are nearly impossible to find and are usually quite expensive when you do find them.

I have used a simple solution in the past which will probably offend the purests here, but what the hell. Modern lugs are quite soft. They are not tempered steel. A 12X24 thread is only slightly larger in diameter and has only a slightly different thread configuration than a 10X24 thread. If you run a 10X24 die over a 12X24 lug you will end up with a 10X24 thread. Trust me, it works.

Larry

The '30s Leedys used 10/24 square head rods.

And yes, running a 10/24 die over a 12/24 rod will work...I've done it...don't know why I didn't think of that in my previous posts...