My sentinel kits didn't come with Hunter-Killer missiles so I had to make my own.
Using scrap sprue, polystyrene, and Apoxie Sculpt I've made the above pieces. Top is the Hunter-Killer on the launch system. Bottom left is the range finder and bottom right is an armor plate. Since I have 5 more sentinels to outfit with these I think I'll be making a mold and casting the rest.
Here's what they look like tacked into place. At the bottom of this photo you can get a glimpse of the custom Lascannon I made out of the stock Multi-Las.