well you have the right way...a workaround way....and then you have the easy way.
the right way would be to find whatever 2pin connection the receiver uses for its fans and then buy some, cut off the ends of the new fan and put on the correct end.
the workaround way is to cut the old fan off of the wires, unsolder the wires from the new fan and resolder on the old wires with the old plug.
the easy way is to clip both wires at the halfway point on the new and old fans and wirenut them together. you could also solder them together and use heatshrink which is a little better.
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before you do anything you should look at the new fan and old fan and compare specifications. do they have the same volt/amp draw? i would try and match this...