which light meter?

Hi,
I use for b&w photography Exakta VarexIIB and Mamiya C330F and I would need to buy a light meter to use with those cameras.
I am thinking on a cheap vintage one (max 40$) and I would like to receive suggestions on which kind of light meter I have to buy and which one you think is the best choice for that price.
Thank you in advance......

P.S.: I already use a porrofinder CDS meter with my mamiya but many times I wouldn't like to change between porrofinder and WLF thatr I prefer for better organization of the shoot.

The Luna Pro is a top notch meter. It originally used mercury cells so you'll need to use zinc air or convert it to a different battery. I believe that Gossen has a kit to do that.