The Pentax one degree digital spot meter is a fantastic light meter. I use mine regularly, but unfortunately I lost its lens cap. I also lost the replacement lens cap that I bought. Then I made a cardboard one which did not fit well and kept falling off. Finally I made a tightly fitting 3d printed lens cap. It is a simple model but really useful.
In case other people find this useful, here is a link to the Thingiverse models. There are two versions: a smooth one and a knurled version that is easier to remove from the light meter when wearing gloves.
This is the light meter: