I have a couple of those silicone pitchers (500 ml and 250 ml, Zuyee brand on Amazon) and agree with
@GemstonePony that they’re great for melting and mixing anything with beeswax. I wouldn’t call mine flimsy, but they are flexible, which seems risky with lye. I think the smaller one would work for pouring batter as long as it stayed clean and dry on the outside. In my experience, silicone gets a bit slippery when “wet” with batter. The larger one would probably be too big for pouring relative to the size of my hand. I feel more confident of my grip when I’m using a pitcher with a handle or a small paper cup (4 or 8 oz size).