Yes, you can use ECR for storing helm charts (https://docs.aws.amazon.com/AmazonECR/latest/userguide/push-oci-artifact.html)

I have managed to add the repo to ArgoCD, but the token expires so it is not a complete solution.

argocd repo add XXXXXXXXXX.dkr.ecr.us-east-1.amazonaws.com --type helm --name some-helmreponame --enable-oci --username AWS --password $(aws ecr get-login-password --region us-east-1)

I'm experimenting with the following (Not yet complete)

Create a secret for an AWS IAM role that allows you to get an ECR login password.

apiVersion: v1
kind: Secret
metadata:
  name: aws-ecr-get-login-password-creds
  namespace: argocd
  labels:
    argocd.argoproj.io/secret-type: repository
stringData:
  AWS_ACCESS_KEY_ID: <Fill In>
  AWS_SECRET_ACCESS_KEY: <Fill In>

Now create an ArgoCD workflow that either runs every 12 hours or runs on PreSync Hook (Completely untested, will try to keep this updated, anyone can update this for me).

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: aws-ecr-get-login-password-
  annotations:
    argocd.argoproj.io/hook: PreSync
spec:
  entrypoint: update-ecr-login-password
  templates:

    # This is what will run.
    # First the awscli
    # Then the resource creation using the stdout of the previous step
    - name: update-ecr-login-password
      steps:
        - - name: awscli
            template: awscli
        - - name: argocd-ecr-credentials
            template: argocd-ecr-credentials
            arguments:
              parameters:
              - name: password
                value: "{{steps.awscli.outputs.result}}"

    # Create a container that has awscli in it
    # and run it to get the password using `aws ecr get-login-password`
    - name: awscli
      script:
        image: amazon/aws-cli:latest
        command: [bash]
        source: |
          aws ecr get-login-password --region us-east-1
        # We need aws secrets that can run `aws ecr get-login-password`
        envFrom:
          - secretRef:
              name: aws-ecr-get-login-password-creds

    # Now we can create the secret that has the password in it
    - name: argocd-ecr-credentials
      inputs:
        parameters:
          - name: password
      resource:
        action: create
        manifest: |
          apiVersion: v1
          kind: Secret
          metadata:
            name: argocd-ecr-credentials
            namespace: argocd
            labels:
              argocd.argoproj.io/secret-type: repository
          stringData:
            url: 133696059149.dkr.ecr.us-east-1.amazonaws.com
            username: AWS
            password: {{inputs.parameters.password}}