I'm in the 501st Legion, a star wars costumed charity organization. I built stormtrooper armor, and it took a while. A few members I know are also members of the r2 builders group. the resource site you're looking for is
astromech.net. Everyone who does runs of parts there does it at no profit. For a top notch one, you're looking at a months of work and about $7000. It's a big project, but well worth it and loved by all. A few of my friends are working on theirs, but it seriously takes a lot of time and effort, and will typically take years to complete.