For using first party Sagemaker images you just need to point to the right image in ECR. Use 1 as the latest stable version to use. Use latest for the latest built.
from sagemaker.amazon.amazon_estimator import get_image_uri
container = get_image_uri(boto3.Session().region_name, 'xgboost')
primary_container = {
'Image': container,
'ModelDataUrl': model_url, #model in S3 bucket
}
create_model_response2 = sm_client.create_model(
ModelName = model_name,
ExecutionRoleArn = role,
PrimaryContainer = primary_container)