Replacing a single Morad-style flanged-rim spoke is a PITA! These rims seem to be ubiquitous nowadays, but I much prefer the Fa-Ba rims on my OSSAs. I found nothing official on the internet that addresses replacing a single spoke. Morad has a website in Spanish (moradsa.com) but there does not appear to be any repository for technical documentation. So it's a bit of a guessing game.
I can tell you that Electric Motion does not sell individual spokes. A complete set of spokes and “nipples” costs $266 USD. Other trials marques as well as parts vendors are willing to sell individual spokes, but you must know what to order.
There are four different styles of spokes:
Short-end disc side
Short-end sprocket side
Long-end disc side
Long-end sprocket side
All the nipples are the same; a turnbuckle style with a right-hand thread and a left-hand thread.
I've been told that it's easier to replace a single spoke on the sprocket side than on the disc side. It's definitely easier to replace an outer spoke and an inner spoke. As luck would have it, mine was the most difficult-to-repair breakage: inner spoke, disc side.
I used a Sharpie pen to mark each turnbuckle so I could loosen them all by the same number of turns. My first attempt was to simply loosen the spokes on the affected side, but this did not provide sufficient clearance. In the end, I had to loosen all the spokes to remove/replace the broken one. Of course, it's necessary to re-true the wheel afterward.