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Adorama has this item available for order:
https://www.adorama.com/mbsppkqbm1.html?
The Speedbooster was initially offered in a Nikon mount,
which wasn't particularly helpful for Pentax users.
If enough people order this one,
Metabones may be motivated to actually produce it.
As of right now, it does have a manufacturer's item code (MB_SPPK-Q-BM1).
In the meantime, you can dream of converting your 100 mm macro
into a superfast tele with enough depth of field to be useful!