The Pachmayr Compac grip is, for me, a comfortable handful without being terribly bulky. The cushioned backstrap adds some trigger reach and absorbs some recoil, and there's support for the pinky finger, but that's about it. I can shoot a steel J frame all day with a Compac grip on it. The rounded contours still let it conceal easily, if that's an issue for you.
If the Compac isn't big enough, the next step up in size is the Pachmayr Decelerator grip, which in the J size is almost as large as the Decelerator for a K frame - it has the same space for your fingers, but is ~1/4 inch thinner side to side. (The K model is also about an extra 1/2 inch taller along the backstrap - to me it is a VERY large grip.)
The size and squishy rubber of the Decelerator makes it THE most comfortable grip I've found for long shooting sessions with a J frame, especially if it's one of the Airweights, and makes one of the little things feel like a big gun in my, not so huge, hands. I usually carry a J frame in an IWB holster and find the Decelerator grips are thin enough to conceal just fine under sweaters in cooler weather, and they'll hide under my Hawaiian shirts in the summer if I haven't gained so much weight that the shirts get tight. (But these grips won't work in any pocket that I have, except those on my large winter coats.)
People talk about rubber grips being "sticky" and not letting cover garments hang freely if you're trying to conceal a gun. I found that to be somewhat true with both of these grips when they were new, but now that I've handled and shot 'em a lot, most of that stickiness has gone away.
If you want a J frame, I'd say go for it and try one or both of these grips. They're each under $25 at Midway and are usually in stock (the Compacs are out of stock at the moment, but are expected in 4 days) , so you won't be out much time or money to try 'em. You can probably get at least half your money back on the grips on ebay if you don't like one or the other. And if you pick a popular model of gun you won't lose much money on it either if you decide it just won't work.
Personally, I enjoy shooting my J frames just as much as my Ks. They're more of a challenge when you get to 20 yards and more (I know, I know, that's not what they're intended for, but still . . . ) but can be remarkably accurate with some work on your part. And small enough to always have with you.