Metabones Speed Booster - allows you to use full frame canon lenses on your M43. I was using this briefly with a GH5 with no issues, although you might need to update firmware on the adapter and the lens to get the most out of it. Just a warning, if you plan on using the with the popular 18-35 or any other APS-C you will have a vignette around the edges, this is for full frame lenses. I ended up switching to native lenses so it's sat on my shelf unused and it fantastic condition.
eBay