where to buy lenses

Hi ,congratulation for this work to everyone involved, you have done a complete work and above all you are it for free! i am electronic from Greece and i decide to make high resolution version.I have printed main body with abs and it came out perfect. Electronics are really easy for me but i am struggling with lenses. I have a rpi camera v1 but i am willing to buy v2. So, can someone provide a cheap source for those 3 optical parts from aliexpress until 20 euros,or from Europe. Also i have not understand, can this microscope operate without those 3 optical parts and only with rpi cam?I have not any idea from microscopes and lenses but i want to make it work