Manual HTM Gunhammers -- production, not HTM custom shop -- do exist, although they're relatively hard to find in comparison to the assisted versions. In fact, now that I think about it, I haven't seen manual HTM Gunhammers in stock at any HTM dealers (KnifeCenter, TNK, etc.) -- I assume because the assisted ones sell better. However, if you order directly from HTM, you can definitely get one; one of the options on the regular order page for the HTM Gunhammers is assisted vs. unassisted.
On DDR knives -- Darrel's full customs (HTM is the mid-tech/semi-production line) -- you can get whatever options you want, including a Maxx Glide bearing pivot instead of assisted opening.