I have a 4" 686 (629 & 617 also) and the most comfortable carrier I have for it is a Galco Vertical Shoulder holster. I know it's not what you're looking for and also not Uncle Mikes cheap but for all day carry, working and walking, it's been about the best so far. You don't even notice it by way of extra weight or getting in the way. Quick access also. I wore an older combat magnum on my waist for a while and it was noticeable after a couple hours. You can expand the system as you please with a lot of optional accessories. If you have other handguns, you can just get the holster and switch it out with the 686's on the system. The 629 and 617 I mentioned fit well also in the 686's as is, all 4" though L, K and N frames.
If your interested, you can see the variations and options on Galcos website, the model numbers but I found the best prices at the time I bought mine was on Optics Planet. I also use Galcos Leather Lotion across all my holsters, belts, scabbards, slings, bandoleers and such. It keeps the leather nice a supple.