Search for wholesale clubs. Commercially speaking, the most conspicuous of these are probably Sam's Club, Costco and BJ's, although you may be able to find smaller, more localized organizations. These types of retailers usually require you to commit to a year membership with entailing fees. However, they often also offer the possibility for secondary memberships to be attached to the primary one at a greatly reduced price.
Browse the Internet. The web is full of different wholesale providers. Sometimes they will be specific to certain types of products such as apparel, electronics, office supplies or other. On other sites, you can filter towards the exact set of items that you are seeking. In order to ensure that the site is genuine and trustworthy, All Business Auctions.com suggests you consider using a mechanism such as Domain Tool's Who-is to confirm their legitimacy.
Consider auctioneer sites. Many times, people post items for auction because they are dying to get rid of them. Whether it is wholesale or a single item, the seller is often looking to get whatever they can for the materials as quickly as possible. This gives you a good opportunity to discover potentially great bargains for discounted or wholesale shopping, especially for business expenses.