To the OP,
in my experience riding an ATV is usually dusty, muddy or some combination of the two.
I'm not sure I'd carry a nice nickel finish revolver out scooter riding, I don't own anything in nickle, so no experience w/ that.
I'd been looking at the Diamond D custom Leather chest holster. The price was holding me back, and I wasn't sure I'd like a chest holster as I almost always wear a windbreaker or jacket. I didn't know if the gun would be accessible etc.
In the mean time I was gifted a Kenai Chest Holster to fit my L frame Smiths. It's a kydex holster w/ nylon staps. I've never used anything but leather for holsters and wasn't sure I was going to like it at all. Well I like it a lot. The straps are wide enough to be comfortable and w/ plenty of adjustment to get the gun to ride where you want it to be. I use it with a 686 w/ a 3 in BBL and a 681 w/ a 4 in BBL. The holster was made for the 3 inch, but the 4 inch doesn't stick out far enough to be a bother.
The gun is very secure, it fits in w/ a definite "snap".
This is just my experience and I'm not affiliated w/ either company mentioned above.
YMMV