How to obtain a tardigrade?
Tardigrades can be found in almost every habitat! The easiest way to find them is probably to look in lichens or mosses (although it depends where you live).

serc.careton.edu website suggests a procedure:


  
  Collect a clump of moss or lichen (dry or wet) and place in a shallow dish, such as a Petri dish.
  Soak in water (preferably rainwater or distilled water) for 3-24 hours.
  Remove and discard excess water from the dish.
  Shake or squeeze the moss/lichen clumps over another transparent dish to collect trapped water.
  Starting on a low obejctive lens, examine the water using a stereo microscope.
  Use a micropipette to transfer tardigrades to a slide, which can be observed with a higher power under a compound microscope.
  


Just FYI, the tardigrades are a sister clade to the Arthropoda (insects, spiders and others). You can find them there on tolweb.org