The following switches are known to exist, but practically nothing is known about them and few if any are still obtainable.
Dai-Ichi are or were a clone manufacturer.
Dai-Ichi Omron B3G-S clone
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 have never found anyone else at AliExpress still selling these Dai-Ichi switches.
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.
Dai-Ichi 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!
Being unbranded, I really have very little to go on with these.
Futaba low-profile linear clone
This picture is from the same gao xiaoqing AliExpress item as the Dai-Ichi Cherry MX clones. These switches are reported to be no longer manufactured. The design is a lot simpler than the original Futaba products.