I don't see notches as much as through-holes. Acrylic is easily cut to specifications by using a CO2 laser. For the design in the video, one could get away with 3 mm thick acrylic, keeping the weight down while providing enough strength for such a device.
Ed suggests polycarbonate, which is stronger and cannot be cut with a laser.
Finding a local makerspace, or posting a query on a laser forum such as Lightburn Software should find you a willing cutting resource. I've done a number of custom laser projects for members of both our local makerspace and visitors to the above noted forum.
Using a service is also a possibility, but the costs increase substantially for established industrial services one would find.