I think there are a few places that have them in the USA. The ebay ad belows claims they ship from California.
Water Cooled Spindle Motor VFD Variable Frequency Drive 2-10HP Converter 34A CE
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Another company in the USA sells these spindles and actually tests the run out and provides a video of the run out on the spindle you are buying he charges a little more but you know exactly what you are getting.
Russ