MacBook Pro (Retina, 15-inch, Late 2013) I need a battery replacement

I do not think Apple will touch it at almost 11 years old. The estimator on that Apple repair site only shows these models being eligible for Apple battery service:

You are left with an aftermarket solution and none are very good. Apple did not design the battery to be user-services. It is glued to the upper deck with adhesives the require dangerous solvents that cannot be used in a retail setting due to HAZMAT, OSHA, and fire codes.

I've seen several reports here of users damaging they Macs beyond practical repair by trying to remove and install an aftermarket battery in a Retina Mac notebook,

Even the company that is the most reliable at supplying Mac replacement parts recommends professional installation, but but the above HAZMAT limitations make even that hard unless the provider has a shop in a non-retail setting with bullet-proof ventilation—like a barn .

You are free to phone Apple and ask them (they won't see your question in this user-to-user setting) but don't be surprised to hear a "no."

This article covers Apple's approach to parts/service for older devices and which are considered "vintage" or "obsolete."

Obtaining service for your Apple product after an expired warranty - Apple Support

Yours is "obsolete" according to that article.

The article mentions battery service possibly being available for up to ten years. However, in addition to "up to," it has an "if parts are available" disclaimer. Only Apple support can comfirm what they can do for that model.

Doll2luve wrote:

I am getting a signal reading: replace battery soon!

That just means the battery's Full Charge Capacity (FCC) is below 80% of its original Design Capacity so that you won't get as much runtime when running the laptop only on the battery. That is all this condition represents. Once the Battery's FCC drops lower, you will see the condition change to "Replace Now" which just means you probably won't be able to use the laptop using just battery power (maybe you will get an hour or so of runtime).

A "Service Now" condition indicates the battery has a hardware issue.

Unless you are unhappy with the battery's performance, you can just ignore the "Replace Soon" message for now. However, if you do use the laptop on battery power and need hours of runtime, then you will either need to have the battery replaced or purchase another laptop.

If you always use the laptop with the power adapter, then just ignore the battery condition unless it says "Service Now".

You may still be able to purchase a replacement battery for this Mac. Check this link for a cost estimate: Mac Repair & Service - Apple Support