The spikes are made to order in DR, you just visit a metalshop like Nino Brodas in Santiago give them a drawing with specs and explain the usage it will have, within a few days they'll have one for you, the actual inner workings are very simple, it's a forced spring plate that will depress when step on from one side and will stay up and punture anything that comes the other way, like a gutter guard on steroids going postal.
If you need the mechanical instructions I will be happy to draw them for you, you just have to change the length to your needs.