Looks to be about a good 1 Inch clearance, converted to mm 25.4mm, so probably some kind of low profile chipset or cpu cooler, of course the specialty low profile cpu coolers all have fans, so you'd have to probe around the power supply and try to pickup whatever voltage the fan wants (5 or 12 volts).
I've since ran cardstock paper through it, making some business cards, the biggest problem I had was that the 2605, even in the Cardstock setting is not real happy running perforated Avery business card stock (specifically for Lasers), but that's not an electronics or 79 problem but a mechanical/paper feed issue.
Before they got bought out PC Cooling and Power Systems used to have an adhesive backed CPU cooler for 486 and Pentium MMX chips, I believe they ran on 5 volts, they were very high quality, and they had a very strong thermal adhesive on it, the hotter the chip got the more it stuck to the processor. I remember having to use a small screwdriver to remove these heatsinks, even when they were mounted vertically. This would be ideal for this purpose, since there is nowhere to drill holes in the formatter board to secure the heatsink, and they were low profile - but they're long gone.
Another alternative may be a VGA cooler, because they're inherently low profile, maybe pull one off a bad or old AGP card?
Here's a link to 3m 8815 thermal adhesive, featuring "high mechanical strength", spec'd at
4.00 kg/in (90 Degree Peel) Aging at 70 Degree C for 72 hrs
Maybe time to experiment.
8810 seems to be available on that auction site, these are the specs:
2.49 kg/in (90 Degree Peel) Aging at 70 Degree C for 72 hrs