I haven't found any with tall switchplates, but I have examples of white SKCM with unbranded upper housings just like blues.
This one is a Northgate 102 from June 1989. Down the page a bit are photos of one from three weeks earlier with blue SKCM. Those dates are from the paper labels added by Northgate after they received the keyboards, so the dates the switches were made are unknown, but earlier than the label dates. Both keyboards are pristine originals and the two sound and feel identical to me.
viewtopic.php?p=386593#p386593
This is a Focus FK-2001 from 1989, also with white SKCM and unbranded upper housings. Also a very clean original. I took it apart to paint the plate but the switches are untouched originals. Again the switches sounded and felt the same as my blue SKCM FK-2001, at least to me:
viewtopic.php?p=475322#p475322
We've proven that Northgate's supplier ("Vendor 111") for the gold badge 102 models was Focus. Based on the Focus and Northgate dates Alps apparently changed from blue to white SKCM in early-mid 1989. Probably too late for tall switchplates.
I have other examples as well, but for the above two I had otherwise identical keyboards with blue SKCM to compare to. One of my long term projects is to try to figure out the sequence of internal changes in white SKCM. That info was apparently documented at one time, but disappeared as older web pages went away. It may still exist on the Asian collector sites, but that's not easy for me to search or translate. White SKCM switches were definitely not all the same. We want it to be simple, but it's not. There's a lot more to it than just complicated/simplified or pine/bamboo. I'm also hoping to tie the changes to the mold numbering on the housings. But that will probably never be a "sure thing" because housings from the older molds were sometimes used alongside newer ones using newer versions of the internal parts.