I just discovered this little jewel and it looks like a good possibility for M cameras with no built in light meter. Priced at $130 USD, it won't break the bank.
KEKS EM-01 Light Meter Review
https://casualphotophile.com/2020/07/27/keks-em-01-light-meter-review/
Available at the end of August from F Stop Cameras: https://www.fstopcameras.com/accessories/keks-em-01-light-meter