Bigrell & CO make plastic pockets, folders and other office supplies. It's the place where I learned HF-welding which is used in joining PVC foils. They have several hundreds of homemade, or rather in-house built welding tools, one for each kind of product they produce. They actually gave me one of their HF-welding machines as a graduation gift when I got my MFA. This place has a special space in my heart. One day I noticed some interesting looking solutions for ventilation and perhaps dripping water.
I think Roffe made these.