My 13 inch MacBook Retina late 2013 speakers blown and made rattling sound, where can I have it fixed/replaced? Should I try to get used parts from ifixit if the Apple authorized store can’t replace it due to replacement parts are not available?

If you have the 13" model, then the speakers are really easy to replace, but you must be extremely careful disconnecting the speaker from the connector on the Logic Board. Sometimes the fit of the connection is really tight and it can pull the speaker connector off the Logic Board even if you are very careful (it is worse for the 2015 model, than the 2013).

Keep in mind the iFixIt part is a used speaker so it is hard to say how good it will be as the iFixIt price is really expensive just for a single speaker (I have purchased a used pair for half the price and new ones are the same price as iFixIt's price for a single used speaker). I have found that the speakers in the 2013-2015 models don't hold up very well. I've been replacing them a lot which is not something I have ever done for any other model Mac. FYI, the speakers for the 2013 model are the same as the ones for the 2015 model which is still supported. Technically it is possible for an independent AASP to purchase new speakers from Apple, but most of them probably will say it is not possible.

If you cannot purchase new speakers, then external speakers are you best option as suggested by @ku4hx since they can be used with other computers as well.

If there are no parts, attach external speakers. That should block the internal ones. Or, you could get a Mac that's less than 9 years old.