Last year I got an Extang Black Max that I thought fit well and looked fairly stock but unfortunately those appear to be discontinued now. There are a few other manufacturers out there that a quick search will bring up but I cannot vouch for any of those. What I can tell you is that no matter what you put on, the average person will never know it's not the correct one nor will they care. Heck, the average person doesn't even know what these trucks are much less what they are supposed to have on them stock, lol.
If you have to have it as original as possible then your options are a used cover, if you can find one, but they do come up for sale occasionally. Also, I don't know if it is possible but an upholstery shop that does furniture may be able to reproduce a new cover that uses your old hardware.