But alas, not fulfilling the game to its full potential. We are a rare breed
I also found the eye-patch when I wasn’t looking for it, but I do like collectables and achievements. To me they are as important as XP and missions are. Without them the game isn’t as rich in enjoyment. I even go that far that I seldom buy a game that has no achievements. But I don’t always keep going until I have everything, like you. 
Funny thing is that now I get the eye-patch all the time. 
Please fix this issue Devs! This is definitely a bug. I know it is RNG, but as many boxes I have opened and come across several duplicates of the same clothing items, there is no way the Eye patch is a truly random item. Given the rate I have found the other clothing items multiple times, I should have found the eye patch 5-6 times by now.
I played with 3 other friends who either found the eye patch multiple times or just once. I got the Fashionista trophy (find 200 articles of clothing) way before I had 200 items, so thought that had something to do with it, so I deleted my game and save file and started from scratch, only hitting the major harbor towns and still nothing after hours.
Either fix the fact that the eye patch is not randomly dropped or place it somewhere in the game where it always will be. This is the last trophy I need and spent hours looking and only finding the same items over and over again.
There is no issue.
It’s just very rare like some other items, too.
It took me about 4 month to get an exp AG4 and I still have no exp sledgehammer after one year.
Getting the experimental ear piece (headset) took me about 10 month, just to mention an apparel. My friend hat more luck, he already got everything of that, the ear piece even within the first weeks. He instead needed much time to get the sapphire green bike while I got it really early.
So yes, it’s just random. But there are many different things in the loot table and none of them are unique (just to get once)… And if you own the weapon packs there are even more items for the loot table.