You
can buy from Amazon US, they ship here. The concern is whether you actually want to, the taxes are nasty. Whenever I order something though, it usually gets here in 2 or 3 business days.
A good quality certified adapter for this scenario would be the Club3D CAC-1088, it costs $42 plus $71 in taxes and shipping:
Club 3D CAC-1088 DisplayPort 1.4 to HDMI 4K120Hz/8K60Hz HDR Active Adapter M/F on Amazon.com
Depending on how much does your credit card charge for the dollar exchange plus IOF tax, you're looking at around R$ 600 for that adapter if you opt to import it, it's simply not worth it IMO, even if you have a high-end credit card with favorable international conditions.
I have found a couple of specialty cables that might do the trick for you on Mercado Livre, but they are also very expensive (R$ 290 with free same day shipping and another that's 225 with standard shipping)
O Lado DP deve ser ligado em dispositivos como computador, placa de vídeo ou Notebook.*Não Suporta GSYNC ou Freesync devido a conversão do sinal DP para HDMI.Lado HDMI deve ser ligado em TV, Monitor ou projetor com porta HDMI.Suporta resolução 2K@144Hz - Com HDRSuporta resoluções até 4K@120hz...
produto.mercadolivre.com.br
- Inovação é na Virtua FX!- Quer melhorar a qualidade da sua transmissão de áudio e vídeo? Apresentamos o Cabo DisplayPort para HDMI UHD, projetado para oferecer uma experiência de visualização excepcional, com transmissão de alta qualidade de vídeo e áudio entre dispositivos.- Precisa de uma...
produto.mercadolivre.com.br
The cheapest one (takes a little longer to ship) might be what you want, the manufacturer claims it's compatible with 4K 144 Hz, as far as I know the cable should be the same (HDMI 2.1 48Gbps), but if it doesn't work at least you can complain. Personally, I use native a HDMI 2.1 cord (Club3D CAC-1372) to plug my 4080 on my LG G3, and my 4080 has 2 HDMI ports, good if I ever need another TV hooked up for some reason.