mouser has a substitute part available:
Something is not right on the mouser website. Look up manufacturer part number RH050R0500FC02 (71-RH50-0.05). At the top of the page in the description section it says "Wirewound Resistors - Chassis Mount 50watts 0.05ohms 1%", which is fine and dandy because that's exactly what we want (according to post #53 in this thread). But then in the specifications page it says "Resistance: 500 mOhms". 0.05ohms == 50 milliohms not 500!!
So I don't know which number to believe - the description or the spec. Is this a typo on mouser? All you EE guys are insane - software is so much less frustrating!