If you don't want to rebody there is only the option of buying joint kits such as the ones done by Parabox. There are other companies out there, you need to search a bit. Especially when it comes to size and skintone.
Then you'd have to prepare the Bratz bodies for jointing, which means you'd have to saw the limbs off at all places you need to be jointed, dremel peg holes and glue in the new joints.
It's very tedious, so finding a similarly sized donor body is often the better option.