Great thread, thank you for posting this helpful information. I just signed up after lurking and learning here for a long time, and thought I would share my notes on this conversion after completing it yesterday and function testing it today.
I did some digging around, and happily this appears to not be the case any longer. I think I might have just created the first true V0 configuration 9mm P30 in the United States over the weekend, with the LEM spur hammer.
I will post pictures showing the different hammers later tonight (DA/SA V3 hammer, bobbed LEM hammer 209321, and spurred LEM hammer 209262), but basically the appropriate spurred LEM hammer is indeed available from both HK-USA as well as hkparts.net (I actually bought one each from both last week).
Everything went smoothly on my conversion. The only issues I had were that I had a slightly difficult time getting the hammer axle out (I did not push the trigger bar down enough at first), and the same hammer axle took some strategic coaxing to get back in when putting everything back together (the punch helped get it through all the various hammer/disconnector/sear parts, but it took some pressing on various parts at the correct angle to get that axle precisely aligned with the far side frame hole such that it would go in).
Getting the elbow spring leg onto the sear while using the V3 sear with that decocker arm was also a little tricky, as well (the decocker arm fights your dental pick for space unless you can figure out a way to hold your dental pick vertically), but I think I could do it a lot faster if I had to do it again, having learned from the experience. A third arm/hand would have helped, though.
When I did this conversion, I wanted the spurred hammer so that I could have a pistol that was in a factory-sanctioned configuration, to eliminate the potential for some uppity prosecutor to accuse me of anything if I am ever in the unenviable position where I would have used this pistol in self defense (it is my primary pistol, so this is a possibility). I also wanted to keep the decocker, so that the pistol would give me extra options by being something of a hybrid LEM-DA/SA pistol where I could carry it like a normal LEM when carrying on my hip, or decock it for an extra measure of safety during AIWB carry. I suspect the hammer spur affords a measure of protection to the decocker button from being depressed inadvertently.
I took it to the range today and put about 120 round down the pipe with zero issues. This pistol already had about 1500 rounds down the pipe with zero issues in its original V3 configuration. It appears to be just as reliable in the V0 configuration, so far.
I do think I will install the heavier trigger return spring that I ordered from HK-USA, along with the light FPBS and possibly the heavy hammer spring. Overall I am happy with the conversion, it did what I wanted it to do (remove the requirement for me to decock the pistol for any reason). About the only result I did not expect was that the decocking would feel a little different. I am not yet sure if it feels different just because the hammer no longer falls during the decock, or if the effort required or accompanying feel to push the decocking button is actually different.
Comparative pictures to follow this evening in a new thread.