I received an order of aluminum encased resistors from DigiKey to try out in my extruder design, and I am happy to report that
P/N RH0055R000FE02 Power Resistors work beautifully. They are smaller than the 10 Watt versions I was using, so I don't know what the durability will be, but so far all indicators are good.
I had seen Emergency Tape mentioned in another post, and just happened to see some at the electronics supply yesterday, so I picked up a couple of rolls to play with. It turns out to be an excellent way to attach the resistor onto the aluminum block of the hot end (a little heat sink compound under the resistor case is recommended).