1994 Other Mazda Models Lost a part

Hi, I was doing my monthly maintenance on my truck. It is a '94 Mazda Pickup b3000. I noticed that the center piece on the front left wheel had fallen off. I went up to Auto Zone the told me it was a "Dust Cover" but they didn't have any in stock and were not able to order me one. The recommended that I try a local Junk Yard. But They did not have any b3000's. And they told me that it has to be the same engine size for it to even fit. I am at a total loss for what to do. I have tried to search for "Dust Covers b3000 Mazda" and nothing comes up that matches my problem. The piece is a Round 3 in in Diameter Rubber piece. It sits in the Center section of the wheel to keep dust of the wheel bearings. Any help will be appreciated.