Lightweight way to send metrics to Grafana Cloud?

I'm looking for a lightweight way to send metrics to Grafana Cloud directly from an OpenWrt router.

I am aware of the "recommended" way, prometheus-node-exporter-lua to scrape/present metrics and prometheus' remote_write to collect and pass them on. But as it happens so often with OpenWrt, flash space is very limited on some of the candidates, and prometheus' 12 MB+ package would not fit. prometheus' write_remote protocol using snappy also forbids some kind of hacky script solution that would emulate prometheus' own remote_write functionality.

I would prefer not to use an external prometheus instance to scrape OpenWrt devices since some of them are deployed remotely. And while I have a perma-VPN connection to those and could "relay" the data, one of the main purposes for me using Grafana Cloud is to see if and when a remote device is down, which obviously will not work if the relaying machine is down.

Is there a more lightweight method to get metrics to Grafana Cloud? Has anyone any experience with that? I must admit I'm very thin on the subject, so I'm hoping someone else went down that road already and made notes in a diary.