Dai-Ichi are or were a clone switch manufacturer. Dai-ichi (第一) means “first” or “number one” in Japanese, but it is likely that these switches are Taiwanese in origin.
These were listed by AliExpress seller harry ke, but by the time I came to order them, he was shipping out genuine Omron instead.
I salvaged this photograph from the AliExpress transaction snapshot for my order, as the current photograph on his store depicts the actual Omron switches that he carries.
This has subsequently been identified as Dai-Ichi CL-1145; I’ve yet to get my hands on a white one, but I have a number of the green ones.
Cherry MX clone
AliExpress seller gao xiaoqing depicts these.
Supposedly these can still be ordered, with an MOQ of 2000. Note the slider — yellow for clone again!
These switches can also be seen in a Micronorth KB-5161 (misreported as Chicony), this time with black stems.