Very easy-to-find. Sold in a variety of paint schemes. As with most of the Tootsietoy Navy, the masts are prone to breaking off. It is recommended that you not try to straighten a bent one.
This looks like it would be a sturdy model but everything except the conning tower has a good probability of breaking off. You often see multiples of the submarine in online auctions, they were in most of the fleet gift sets and probably were the least expensive to buy individually. Wait for a good one, every fleet needs three or four subs for protection.