I found my trucks on eBay. These were hard to find, the 580 size (I'm riding these now, about 2.75" of truck between the wheels. I have the 500's (these are around) also found on eBay. I see lots of Bennett trucks. I think Independent still makes a small truck for freestylers. Maybe freestyle skateboarders have resources for narrower trucks. And of course, Tracker's mid and half tracks are around, maybe in magnesium?
Very happy to have a place with contacts to other rollerskaters!