Individual track links are usually injection molded (like the rest of the plastic model) or sometimes are resin. Becuase ot this, they have a higher level of detail and accuracy than the vinyl/rubber ones (I think they even make some in white metal also, for a very realistic look). They take longer to assemble as you are gluing indiviual links from the track together. Sometimes you can find them for a fair price, but usually the nice ones will cost as much or more than the model you are putting them on. All good model stores should have some, if not, all of the big model retailers on the internet sell them, for example, www.squadron.com. Just do a search under 1/35 scale (or whatever scale you want) armor accessories.