There are a few women on SG and badkity. I’d also look at photoacompanhantes - the appropriate search terms should be somewhere above. SPlove, barravips, and private55 are interesting sites to find women on the spectrum from fit to very fit. Porto Alegre always has a few gems but it’s a bit out of the way if you’re doing the SP —> Rio trip. Twitter can also be useful - I occasionally look up iluvmusclegirl to see who he’s reposting as that’s a decent indicator (especially if there’s a WhatsApp link on their profile).
Otherwise, in person, your best bet in SP is clubs like Bamboa or Scandallo. By no means are you guaranteed to meet a bodybuilder; however, there are usually a handful that catch my eye as extremely fit women. In Rio, I’ve been to 4x4 a few times which is very fun. I do think there are more of your bodybuilder types in 4x4 than the SP clubs, which is probably attributed to the much warmer more-outdoorsy climate.
I’m not sure what we’re allowed to say on these forums so DM me if you have more specific questions. Wouldn’t mind creating a telegram or something in the event our trips overlap in the future.