I agree with alvin. The net is the best place to get parts. Tower is good and reputable.
But if you are willing to take the risk, you can order from those fleabay chop-shops (guys who more or less illegally take a Cenchain RC, tear it down, and resell the parts).

I have so far had good luck with the fleabay chop-shops, but I don't buy from them anymore because I object to their practices. Yes, they buy the Cenchain RC legally, and it is theirs to do with what they want. But depending on their state laws, it might be illegal to resell a product they previously bought for a profit without a vendor's license and proper tax ID. I personally cannot support that, but if you choose to buy from these unauthorized chop shops, they are probably the cheapest source for Cenchain RC parts.