Here are lenses I can recommend:
21mm Voigtlander f/4 P
21mm Zeiss f/4.5
25mm Zeiss f/2.8
35mm Zeiss (either, f/2.8 or f/2)
50mm Zeiss Planar f/2
So yes, you can save a bit of money buying the alternatives and have great photos made with your Leica M camera. Buying them second-hand is an even better option for cost savings. Don't sweat it!