Take a look at that manual and see if there's an email address that ends in 'smith-wesson.com' and send that address a note.
Their Customer Service has always had a 'live' person answering whenever I've talked with them.
If you sent in your Warranty Card, they're serious about making you happy, and if you haven't - send it in now and wait about a month before you ask about parts.
They'll do the needed work and they'll send you a Shipping Label that covers associated costs through FedEx, so there's no out-of-pocket expense to you, and their turn-around is fairly fast.
That being said - they only warranty for standard ammuntion fired through an un-modified revolver, so if you did anything to make BP easier to use, you likely voided the warranty.
It's my understanding that S&W has a 'very' limited number of spares, since the weapon's discontinued - they supposedly sold what spares as there were to Numrich - though I've never seen them listed.
Good Luck!
Vaya,
Scouts Out!