OK. So, unless you're an optics expert that can build your own parts, you'll be best off modifying something that already exists. Because optical sights with magnification are pretty complex, that will most likely mean only modifying the outside.
So, first off, do you want it to look accurate? That probably won't be possible using any existing handgun scope, and it will have to be a handgun scope because a riflescope will not have the correct eye relief.
You might be better off trying to achieve this with an ANH hero DL-44... you're much more likely to find a handgun scope that at least has the correct profile. The tank scope used on the ESB DL-44s was actually designed to be used in a periscope, and is very different in profile from any handgun scope that I'm aware of, which will make optics you can actually see through more difficult.
I'm not saying this is impossible, but it will be pretty difficult if you want it to remain accurate in appearance.
Not having magnification will make things much easier, but keeping an accurate appearance will still be difficult.