Unless something has drastically changed recently, you can order the parts to create a dummy Fusion surface mount. I would order the heads from a lightstick, (400 series or above as the 100 and 200 use heads with internal flashers). The lightstick heads are designed for exterior use, where as the heads from the interior bars and dash lights are not. You will also need the flange and gasket. There are no dummy cannons that I am aware of.
Be aware that they will come with plugs that will need to be removed unless you can find a mate for them. Doing so will void the warranty. Keep in mind that your Feniex dealer or rep may tell you that cutting the plug will not void the warranty, but there is a good chance that if and when the head has an issue, tech support will not warranty it. Speaking from experience.
Sorry, I do not have the part numbers for you. To my knowledge, Feniex no longer produces a complete parts listing for their products. They did one year and it was awesome.
Hope this helps.