If you have a pin in the sight boss of your 686, it can be changed out by drifting the pin out and installing your new sight of choice. S&W offers a pretty good selection of sights on their web site so that's one place to look for a new front sight.
You also should know that there are 2 different interchangable sight systems offered by S&W. The simple pinned in sights and the DX sight system. On the DX sight system the front sight is in a spring loaded sight base, so changing the front sight is a simple matter of pushing the sight blade towards the rear and tipping the front up and out of the mount. The DX sights can be easily identified by a small bore in the front of the sight rib above the muzzle. I doubt your 686 has a DX sight, however on a PC model it would be quite possible. My 610 has the DX sight and I think it's a great system, no tools needed and the front sight can be changed out quickly right at the shooting bench.
As for me, I've now gone to reflex sights on my revolvers. Do almost all of my shooting at indoor ranges and the lighting at most indoor ranges just doesn't work for aging eyes. With a reflex sight I can once again so a bit of "schooling" of the youngsters. These are NOT cheap, however shoot with one and it won't be too long before your buying more. Check out the following link if that interests you. Purchased 2 more J Point Reflex sights, range report.