Rare items are sometimes spawned during an event, as a reward, but it is quite rare and didn't happen in some weeks, now.
There are hundreds of Light Support Weapons in game. I can't say if it's craftable or not but there is obviously some way to get some - maybe merchants were selling it some time right after wipe. We often think items are rarer than they actually are, because players keep them hidden in tents or bases and never use them.
