Dyson DC18 parts are available to buy online at Dyson's website, VacPartsWarehouse.com, Vacuum-Direct.com and Appliance Factory Parts, as of March 2015. The latter three websites have the most extensive selections.
Parts include major components such as the motor, cyclone assembly, brushbar assembly and wand. Minor parts include specific screws, seals, cords and filters.
VacPartsWarehouse.com, Vacuum-Direct.com and Appliance Factory Parts display exploded diagrams of the core parts of the DC18. Beneath the diagrams are the lists of parts available. VacPartsWarehouse.com and Vacuum-Direct.com integrate the diagram with the available parts, numbering each part and placing a purchase link next to it.
Appliance Factory Parts also has a large selection of DC18 parts, but only some of the prices are available because the website gives out the prices only upon email request. Dyson's on-demand selection is smaller, but buyers can order more parts by phone.