How do I select replacement parts?

I have tried to look on amazon, ebay, and just the whole web, but I couldn't find internal parts like the one you listed. Or maybe I haven't looked close enough...

I've found a phone of the exact model that's being sold for parts on ebay, though. It's actually a whole working phone, but the only problem is that it has problems with activation, which I'm assuming refers to cellular plan. It's selling for $20 and free economy shipping (at least for where I live) and can be found here. No matter how much I try, though, I can never find a guide for taking it apart.

Hope this helps!

Edit - this item is now out of stock. There is a new one for $66 dollars, but it is the exact same one as the one that @osa1011 has in his answer.

Unless you already bought the $20 phone.

I see the NUU X4 for sale brand new on ebay for $66. It's probably going to cost at least that much to fix the phone since you'll probably have to replace the digitizer to get to the headphone jack, not taking into account the fact you won't be able to get replacement parts for this device. A phone that sells for $66 doesn't have a market for selling repair parts. Usually for a phone that isn't iPhone or Samsung, your best bet is to buy a broken one that has a different broken part.