Most of the supplies you need for an altar don't have to be purchased from shops selling metaphysical supplies. In fact you can buy everything you need in Walmart or in a thrift shop.
Some items can be found in the most common of shops. Such as Walmart, Hobby Lobby, Michael's, or flea markets.
There are most likely metapysical/pagan/wiccan stores in your area. You might not know of any, but they are there.