I know this will be much more expensive than the G-Penny, but consider a spindle from CNCDepot. (cncdepot.net)
They have a front mount 3Hp (2.2 kw) ISO 30 ATC spindle. " FM30F - 12,000rpm (400hz: 4-pole motor, for higher torque at lower rpm*)"
Considering many Haas machines max out at 6K RPMs, these are still spinning pretty fast.
They also have a mounting plate for the 1F Z-20