To the dump mate.
There are several different organizations that sell wheelchair ramps, and it's hard to determine who is the largest provider. It's important to determine the specifics of the ramp needed before ordering.
There are several online sites that sell used wheelchair parts. You can also check with local stores for wheelchair parts.
Furniture stores that sell restaurant furniture will also have wheelchair accesible tables. You can also have a table custom made to be wheelchair accesible.
You can sell crushed aluminum cans at a metal scrap yard in your area. Most of them will pay the going price for aluminum by the pound.
Here are a couple places that sell them: http://www.usmedicalsupplies.com/Scooter-and-Wheelchair-Lifts.htm and http://www.ameriglide.com/ .
There are several websites that sell aluminum bar grating. Local hardware stores may also sell aluminum bar grating.
There are many great online companies that will sell homeowner installed wheelchair lifts. One online company, Ameriglide, will sell you a lift that includes up to a 10 year warranty.
A very reputable company that rents wheelchair ramps is American Access. They also have 24-hour installation services and you can order online. They can have the ramp delivered and installed for you in about 24 hours, so they are a great choice for emergencies.
Contact any power wheelchair sales in your area, they usually sell the lifts also. You might also contact an accessible vehicle dealership they sometimes sell vehicle lifts. One note of caution be sure it will safely carry your chair. If you have someone who is handy to install one for you that would save you substantial money and you might find one on ebay or Craigs list at substantial savings. Hope this is helpful. Jan in TN
A company that is geared toward handicap accessibility would probably sell wheelchair vans. Such as Rollx van.
BAD QUESTION (auto maker not specified)
There are various stores that sell parts for handicap van wheelchair lifts. One such store is VCI Mobility which is located throughout the US.