Hi Marzanna,
In my modest experience, you will almost certainly never find the exact objective design unfortunately, and it is in the interest of the manufacturer to make it hard for you to even find the related patent of a known objective lens. And even if you manage to find the patent, the design you’ll find in the patent is probably not the one that has been chosen for the final product.
Patent search is difficult, I found that searching through Google Patents is a good option. I usually use the parameters of the lens such as magnification, NA, working distance, and the manufacturer (Zeiss, Nikon, etc...). Lately, I posted something about a Zeiss 20X lens:
Knowing that Zeiss is a German company, it was likely that the patent was filed to the German register, but that is not always the case. Can you tell me which lens you are looking for? Perhaps I can have a look and see if I can find something relevant.
Take care,
David