There is no contemporary 24mm lens for your Leica - the widest contemporary lens was a 28mm f6.3 Hektor. The only other screw-thread lens wider than 35mm was the 28mm f5.6 Summaron, which is a nice lens, a bit younger than your Leica, unfortunately sought after by collectors and so more expensive than it is really worth.
Originally Posted by kavandje
There are new Zeiss lenses in Leica M mount, not screw mount as far as I am aware. A lot of people use the Voigtländer 25mm f4 lens, readily available new or used for not too much. You can also fit Nikon SLR lenses or Pentax M42 lenses via adapters.
If you want a contemporary lens, you might find a Canon 28mm f3.5, but this will not be cheap if in good condition. An 85/90 finder should not be hard, Leitz finders secondhand but a bit expensive, Voigtländer new or secondhand, not too dear, also some older finders from Braun, Kodak etc. Not too hard to find.