I have nothing against second hand trading, but the typical implementation which rewards a mad dash, combined with too cramped locations, is a recipe for semi-disasters. In last Tactica, I physically and literally couldn't get
out of the area, never mind actually buying a thing. Wasn't even carrying a rucksack. It was a set-up you can read about in newspapers when something goes wrong and people get killed.
A few hours later there will be room, and plenty of broken plastic space marine kits at store prices to choose from.
There may be a better way, but if the stuff is limited by definition, the only way to avoid a "first come" rush is an auction, and those are better handled online anyway.