I'd shy away from anything but Genuine Toyota. There is probably nothing wrong with your fan clutch other than, like mine over the past two decades the oil has leaked out and broken down so while still working it is ineffective. I got a 18ml tube from Toyota for $11.00 part # 08816-03001 and a new O ring from a local auto parts guy. My fan works like it should now, other than the PITA to take it off and back on it was a cheap repair. In all honesty flushing the radiator would be easier, like I said start simple/obvious but your symptoms are very similar to mine.
