somafunk - wot trail_rat said.
The fan needs to be able to draw cooler air across the heat sink to maintain the temp differential across the peltier device faces. However, FYI, mine has a footprint of 10cm x 8cm (w x d) with the fan out sitting out the front an extra 20cm x 4cm (w x d)
I reckon it would probably just work on yours if you set it on top to one side so that it could draw some cooler air from to the side of the stove. Mine works at relatively low temp differential but obv spins much faster at optimum diff.
Also, how hot does the top of your stove get? Mine runs at between 100 and 200 deg C