There are many fine options out there.
Slight nod for me -- with distinct caveats -- goes to the Alessi Deep Cover. It's specifically made for J-frame snubbies. The leather used is very thin compared even to most horsehide holsters, which is great for not taking up extra space, yet whatever they use to cure it keeps it exceptionally strong and resilient. I've been wearing one daily for a couple years with no discernible wear. Form-fit and holds the snubby well.
Two things, though, make the Deep Cover a standout for me: it's a low ride holster, which is harder to find for IWB, and it has the best clip I've ever used. The low ride allows the J to sit deep in the holster and very low in relation to the belt line; only the grip shows, barely. This makes for slightly more demanding hold when drawing, but in return it is notably better for concealment.
The clip used is designed to hook onto your pants, behind the belt rather than over it like most conventional clips. Result is you don't need a belt and the holster hooks securely and stays in place on draw, and since it's behind the belt it's that better concealed. Truly a top design.
The trade-off in choosing an Alessi Deep Cover, at least when I dealt with them (and I've encountered the same complaints from others since), is Alessi won't get your order out in the timeframe they claim, won't initiate communication any step along the way, will be hard for you to get in communication with, and will have bogus excuses why your holster isn't ready -- though it will eventually arrive.
It's a crummy trade-off, and only worth it if you have the time to wait and don't mind not knowing anything about how it's going. In return you do get what I think is the best J-frame IWB you can buy if consistent concealment regardless of build, garb and physical activity is your primary desire.
Every bit as good but in a higher ride configuration and with a conventional belt clip is Lobo Gunleather's Offset Belt Clip. It's excellent and equal to the Deep Cover in every respect regarding quality built. The higher ride slightly compromises perfect concealment in lighter garb or when leaning or bending over even in heavier clothing as all higher riding holsters will, but also makes for easier reach if you have to pull compared to a lower riding holster. The conventional clip does have to go over the belt.
Lobo Gunleather, a highly regarded member on this forum, has a well-deserved excellent reputation regarding the buying experience: professional, highly communicative, and fast turnaround, especially given the excellence of the product.
If wait and good communication are not an issue but top-quality and concealment for every occasion is, Alessi's Deep Cover might be for you. If a higher ride IWB is preferred or at least acceptable, and top-quality and tier-one customer experience are valued, Lobo Gunleather is the way to go.
Good luck; let us know what you do.