Now seems to be working by following up the tool install with
helm pull rancher-charts/rancher-monitoring --version 107.0.0+up69.8.2-rancher.15 --untar --untardir ~/charts
helm upgrade --install=true rancher-monitoring ~/charts/rancher-monitoring --namespace cattle-monitoring-system --timeout 10m0s --values=~/charts/rancher-monitoring/values.yaml --labels catalog.cattle.io/cluster-repo-name=rancher-charts --version 107.0.0+up69.8.2-rancher.15 --version=69.8.2-rancher.15