What other fan than a 4" Spal Puller?

Got (need!) an IMS 27L (7 gallon) large tank mounted.
This tank leaves too little space for mounting a 4" Spal Puller fan, which is a darn pity as I want/need one mounted. This Spal is too high - therefore I want a lower-profiled one.
Yeah, I've read about somebody mounting a PSU-fan out of a PC, but I don't like this. These fans are not environmentally sealed (not reliable for this purpose), and also they move little air compared to an automotive/bike fan. Oh, a high current draw is not a problem for me.
If anybody knows of a fan which might/will fit - around 4" diameter with a lower profile than a Spal - please shout here?

Also, for controlling a fan one needs a thermo-switch. I've got one here, ordered online based on the switch-temp, but what I got is a rather large thing. If someone knows about a nice small/thin/short unit, which switches somewhere around 100 deg Celsius, then by all means tell me too - even if the switching current is small, then I'll simply add a relay.

Of course, if you've got any sizes - of fan or switch - they will be welcome.