Greetings;
I've had the same problem with my new Soma 'Groove' and a new (FREE) SunTour fork. After much net searching, the shortest stack height I've found is a 26mm FSA TH-857, currently $25.00 here in the Colonies and I'ts not a bad headset. I can't help with the stem as I'm using my retro Specialized titanium 150mm and 37mm(whatever happened to Imperial Measurements) where it bolts to the steerer. I've not used spacers, bolting the stem directly atop the headset. Good luck with your build.
Regards