You can't find much because there's not much to find.
Tritype is only discussed by a particular duo of theorists (the Fauvres). That's the 584/583 stuff. You might find more on those tritypes on the 5 forum, and you can find 4 vs 3 stuff on those forums. But I doubt you'll find much on sx/sp stuff particular to 58* tritypes, and you certainly won't find any official-sounding information about what it would mean to be a 584 sx/sp ISTP specifically. I don't know of any fancy lit about MyersBriggs Enneagram combinations (unless we want to count Naranjo's cognitive function correlations, which iirc included no in-depth analysis), just random online people's opinions about them. You can ask what we think or believe, but afaik there's no book about ISTP sx-first 5s.
You'll have to stitch all your typings together yourself. Just like the rest of us.
Well you'd have to look up both fours and threes to see which tritype you identify with. However Madhatter did compile a list of threads nottoo long ago, but looking up your individual heart fix first before going there is best.
What are you struggling with exactly?