Your 686 can be changed to a patridge. How much work or cost is involved depends on how its red ramp is attached. If you have a newer 686 it’s relatively easy to drift out the pin and pin in a new patridge. If you have an older 686 with a sight blade that was forged integral with the barrel a milling machine is required to remove the old sight and mill the slot for a pinned in blade.

There are other ways to install a patridge like milling a 3/8” dovetail across the barrel rib, but milling in the slot for a pinned in blade would look most similar to a factory installation.