Well, there are a few different ways you can go. Because you want a lens that get get close to the subject, I'm going to assume that you have the camera sitting on the desk/table in front of the set, the same way I've done it for the last couple of years. This method although easy when shooting, will make your search for lens/lenses a bit trickier. The only lenses that are going to be able to focus close enough to the LEGO are macro lenses; they'll be able to get about the same distance or a little closer than the one which you are using now. Now be aware that almost all macro lenses are prime lenses, meaning they do not zoom. If you were able to find a zoom macro lens, it would probably cost way more than I would guess that you are willing to pay. Another option to consider is that of manual focus lenses, as apposed to today's auto focus lenses. This is a relatively complicated topic, and I would ask you to wait a week or two, because I'm currently working on a video which explains this. A third option is sticking with the lens you have, a lot a brickfilmers use it. I'll post a link here when I've finished the video. 