Interupter lever can pe used on their own. The cable end rests at the brake lever body

It's a XB3 ('73, soviet union) aluminium bar, 25.4mm all around (stem area + straight part + straight parts on the drops, the curved sections are a bit deformed out of circle so it's hard to measure a diameter - I guess it's a standard 1" pipe rolled on a primitive machine that bends it a bit out of round) - I like this one as I have cool memories with soviet bikes and the fact it's the handlebar from my first semi-road bike, and the fact that it's only 290mm wide.

At least BMX cult is on the rise and a few shops are stocked with them (I'll check them tomorrow, right now is late in the night), around here mtb is the thing that any bikeshop has. Road biking is marginal but still common. Fixie/single speed/IGH are a tough one. I scraped the whole country for a fixed gear cog and stick with a threaded cog made for chainsaws for a while until a month later I found a proper fixed gear cog 400km away, forgotten in an old man's magic drawer. So this cross lever that was looking for sounded a bit like the hunt for the fixed gear cog. I hope i'll find a proper bmx lever.