Where can I purchase an aloe Vera plant?
Sometimes the garden section of WalMart or any major hardware store like Lowes or Home Depot. Assuming you live in America.
heart o' gold
At your garden center or on line. They may only be available seasonally depending where you live. In my area Aloe grows really well outdoors and I can take cuttings from established plants in the area. I keep plenty of aloe on hand because I do hot glass work and use it to treat burns.
Go to any nursery. They should have healthy plants.
Most any garden supply shop.