indeed.
I have over 500 non-TCG Seviper items already, but 1/3rd of the time I’m looking for items from my wanted list that I have seen before, I come across completely new items I had never seen before prior. At this point, it honestly wouldn’t surprise me if there are 500 more Seviper non-TCG items out there (including the 81 currently on my wanted list). 
And as you mentioned, information especially is even harder to find than more of these items themselves (although the same could be said for some ‘unfindable’ TCG cards). Heck, sometimes the product of an item when you have it in hand already proves difficult to determine, although luckily there are some amazing members whom can usually figure that out.
I guess that’s also one of the big reasons why I enjoy writing my articles and collection posts with all the information, to help other collectors in the future who are looking for release information like I did. 
(Although I also do it as documentation that’s easily accessible for myself tbf.)
Greetz,
Quuador