I would find a local IH/Navistar truck dealer. Take the original one (which is an IH part) or tell them you need a glow plug controller for a 444 Diesel engine. Not a T444E that's a 7.3PSD......
Original part for less than Ford.
A little tip, go find the "old guy" at the parts counter. I went in for a fuel filter for my IDI with a part number. When he came back with it, he said "That's for an old 7.3 IDI.....". I told him it was and in a Ford pickup. Told me he can get parts for them, and if I didn't have a part number he would just look in the 444 parts book.....
Most of the time, they are the least expensive option for a local parts pickup (for OEM parts)....... plus my local IH parts counter opens a 7am Monday and closes at 3pm Saturday......