I used an old 12v avionics cooling fan I had lying around. Like this:What fan and thermostat did you wind up using?

Cyclone 100 - 1 Port Blower (14VDC or 28VDC)
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You might find one cheap on eBay, lots of versions and most have the 5/8” output.
And this is the thermostat: https://www.amazon.com/gp/aw/d/B0C282MRM6?psc=1&ref=ppx_pop_mob_b_asin_title
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