For those of you who own D'Shannon Tip tanks, I talked to Scott Erikson at D'Shannon.
He too, recommends the $32.50 led lights from Aircraft Spruce that Tom Pelz above listed for the tip tank nav lights. He did say however, D'Shannon does not currently have a solution for replacing the strobes in the tip tanks and they are actively looking into it at this time.
I am planning to repl the tail, right and left navs in the next week or so. I am hoping to replace the upper and lower beacons and landing lights soon. Whelen wants $538 for each upper and lower beacon and the landing lights are going to run $650 for both.