Usually installation supplies and tools are available to installers through local distribution centers as the installers work for a company or have a business license and can purchase wholesale. Even as a volunteer, you should have a business license and be bonded against injury or damage.
Without a business license check out retail satellite sales websites such as Galaxy or Sadoun. Not a large selection or the best prices as they are retail. Many folks who do purchase smaller quantities of supplies and tools use eBay. Some real great deals on name brand install supplies.
If you have a business license check out:
www.perfect-10.tv or
www.skywalker.com
Local Electrical Wholesale Supply centers such as
www.platt.com or
www.graybar.com
RSI and DSI seem to have left the Satellite Supplies and now distribute flat Screens and mounts. Avoid home warehouse stores such as Home Depot or Lowes as their prices are very inflated and items usually are often not commercial grade targeting the home DIY in small quantity packs.
As Glorystar systems include most major supplies, you only need to supplement with a spool of bulk Quad Shield RG6, UG rated Quad Shield RG6 (for underground), matching F-fitting compression connectors, ground wire, cable clips for wood, metal and vinyl/metal, 3GHz wall plates, pitch pads, cable stripper, compression tool, long drill bits and a stud finder. Should be able to pull these items together for $200+.
No install kit is complete without a sighting compass/inclinometer (or one of the new smart phone Dish Pointer apps).