Low-density materials containing tracer elements are an important component of target platforms for high-energy density physics experiments. High-Z elements can be dispersed homogeneously by changing chemistry of the matrix or by simple physical mixing; alternately, tracers can be introduced heterogeneously in the form of ultrathin foils or particles. We have recently focused on how best to manufacture and embed tracer elements into silica aerogels and polystyrene-divinylbenzene (CH) foams. The ability to control dopant concentration and distribution is critical to final shot success. We have produced low-density CH foams doped with chlorine at levels up to 2 at. %. In addition, we have placed metal particles and foils precisely within silica aerogel monoliths.