Cause replying to your own posts is cool and trendy...
I actually managed to hunt down a store that carried them, though they had the K502X rather than the K503X. And that thing was massive. Thicker and longer than my Charge and fairly weighty.
But they also had the E307X, which is essentially the same thing minus 0.3" of blade length. It also had the Leatherman fast open feature, a liner lock instead of a lockback, and no can opener (which in my experience aren't actually very good at opening cans anyway).
Size-wise, it's about as thick as the Charge, a little thicker at the tool storage bulges, but it has less volume and is half the weight, which makes it more comfortable overall to carry. I measured the maximal thickness at about 23mm, not including the pocket clip.
On a plus note it has a good blade, the bit driver is very useful and the handle ergonomics are very good for a multi-tool.
Unfortunately the pocket clip is facing the wrong direction and there's no way to reverse it. My biggest concern though is the tip of the blade seems to not be adequately recessed and it has caught on fabric a few times. Hopefully it won't deploy in my pocket, because that would be quite uncomfortable. The tools are also not lockbacks but are reasonably secure.
There is also a good deal of wasted space where the can opener is on the larger models. It seems like they could've included it on this model, though I'd prefer the ultra-small bit driver of my Charge that works on eyeglass type screws.
Overall though, it's quite the refinement of the SAK-type profile multitool knife, being first and foremost a knife. After EDCing my Benchmade 806D2 AFCK for quite a while the only things I wished I had with any frequency were screwdrivers and an occasional bottle opener for beer.
The Charge wasn't a very good replacement for a dedicated folder to add some tools, as the handle ergonomics are terrible and the blade is pretty sub-par. Additionally, there are a ton of tools on it I'd just rarely/never use, so carrying it around when it felt too heavy/bulky seemed like a waste.
The Skeletool is also upcoming from Leatherman, and is about the same size and weight though thinner, with a slightly longer and narrower blade, and a rather interesting design that also gives you pliers (though it loses a bit driver storage slot). The pliers I would occasionally use, but it seems to compromise the ergonomics and more efficient blade shape to do so. Sort of like the Charge. I might pick one up but I'm not sure.
I could've also just carried a smaller multitool like the P4, but that would've pushed the total weight up to the Wave range, and I don't like the P4 on my keychain and don't like carrying around more loose stuff. Seemed like I might as well just carry the Charge and get better tools.
Anyway, guess I'm rambling here, but I like it enough to be my EDC for now. Decent if minimalist tools without overly compromising the knife aspect of things.
EDIT: I also wanted to mention I got it at Sportsman's Warehouse for $45. It was stickered at $80 but rang up at $45 and it's the right item on the receipt. Pretty sure they're on sale so you if you're interested and have a SW in your area you might want to see what the price is -- $45 is less than what I've seen it for online.
Seriously though...thanks for the info on the K503X. I have a couple of the smaller Leatherman knives and I have been thinking about buying one of their larger knives.