You can still purchase and use digital answering machines and some phones have them built in but most people use the voice mail that comes with their phone service.
Most stores that sell telephones also sell answering machines. Department stores like Wal-Mart sell brands like AT&T models for around 14 dollars. Office Depot for about 19 dollars.
Yes, digital answering machines can still be bought and used. Many places online still offer them at reasonable prices. Wal-Mart and electronic stores, such as Best Buy also continue to offer digital answering machines.
They are still available, as they can still be used with home phones. The selection is quite limited, though, because of their decreasing popularity. If you can't find one in a store, try searching online.