OK for the cheapies.....The originals are at the woodland scenics site
here and go to
"terrain" then to
"Rock molds". They are about $8 USD each. they are very durable and reusable. OR just send the money for materials or send the materials and I'll make them for you useing my molds. Now if you find that
"one" rock you just wanna have on every base here is how to do it cheap(ish).
Castin craft mold builder liquid latex 
Buy Castin' Craft mold builder ($15 USD for 16 OZ)
Follow directions for 3-4 layers
Lay guaze OR webby type cloth material for stability
apply 3-4 more layers of mold liquid
now you will have a mold for the rock to use over and over. This process TAKES FOREVER THOUGH!!! and for the price of WS molds its worth it to me.
