Something thin and copper like this, could be easily cut using a rotary tool (dremel) or even a hacksaw w/ some patience, then drilled and mounted to the board.
You're seeing the limits in the design of the chipset heatsink; it was not intended to see active ventilation, and it's 'bulk' is compensating for lack of surface-area and the material used.
TBQH, w/o changing the cooler, you'd be better-off using a 'centrifugal fan' like out of a laptop or single-slot GPU cooler.
If you meant 'Peltier', just don't. (At least not in this application. Get an old board/build to 'play' with Peltier devices (TECs), if you're that curious.)
Without regulation circuitry, you easily could get condensation and short something, or under-cool the TEC and burn it out, followed by an overheating/dead chipset.
Either way, there's a ton more bulk; which is already something trying to be avoided.
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