My suggestion is, once you find a reliable vendor that ships via turkey post ($4~$9) buy a few extra cells, in case you are planing to grow your collection. Liitokala have very good 3500mAh batteries (either based on the sanyo GA or samsung 35E, can't get a confirmation from them), the Lii-35A. I got 4 when the official liitokala store was shipping to Brazil for a while, regret not having bought more. My last batch was a bit more expensive, both the cells and shipping. But you might get lucky.
Here are the links of AE stores I have ordered cells before, bare in mind that most don't ship here anymore:
MAN BUY Store (sells Nitecore products, cheap shipping, VERY expensive batteries)
manbuystore.aliexpress.com/store/1934124
China Electronic Store (ordered one cell, never arrived, got refunded, should've know better)
aliexpress.com/store/513871
Best Power (sells keeppower and nitecore batteries, somewhat expensive)
aliexpress.com/store/918105
Liitokala (oficial liitokala, most of the time does not ship batteries to Brazil, but I managed to buy 6 cells here once, fairly priced, but shipping is unavailable most of the time)
liitokalahongkong.aliexpress.com/store/217753
BlueSeni Store (I'm waiting 6 cells from this seller, but does have shipping to Brazil anymore…)
13760394452.aliexpress.com/store/3113003
Lucky Electronics Store (also waiting for more cells, also stopped shipping to Brazil since I made my purchase)
aliexpress.com/store/1191644
I'm also thinking of buying a couple of cells from RTD Vapor, who said could ship to Brazil, just not via their e-commerce
As you see, most of them are one-shot, I've bought cells where I found opportunity. Unfortunately, I know of no better or sure method for doing so. Oddly, I can find and order 20000mAh+ battery packs with ease...
Another option is to salvage used notebook batteries, you might get lucky with cell quality/capacity if it's not too old