You can try Academy, but I doubt if they will have it - but you never know. Bass Pro Shop is a better bet if you have one close by. Wal-Mart will not have it. If you have a reasonably well-stocked private local gun store, try them, and if they don't have any, see if they will order it. It can usually be found at gun shows. Last resort is that the internet ammo guys will have it, but shipping is a little high. Don't be surprised if the price is going to be somewhat higher than .38 Special, just the price of a round that there is not a lot of demand for, so it's sort of a specialty item.

I shoot .38 S&W a lot, but I reload mine. In your gun it can be handloaded to near the performance of the .38 Special, but the factory load is a lot more anemic due to the large number of weak 19th century guns in that caliber still floating around. It's one of the earliest centerfire calibers still being factory loaded today.

Your grips are aftermarket replacements. That type of grip is very common, and a lot were sold in the 1950s and 1960s. Nothing is wrong with them other than they are not factory original. You can find original wood grips for sale lots of places if you want to spend the money. I wouldn't bother. Just shoot it and enjoy it as it is, as it is not in collectable condition.