Alternatives to 13mm diameter / 5mm focal length PMMA lens

Sourcing the 13mm ø / 5mm focal length PMMA lens is proving difficult (the only vendor on AliExpress is not shipping to the UK).

Is there any way to substitute a more easily sourced lens into the design (e.g. something from the Edmund optics catalogue)?

For anyone starting out building just one microscope, this would be much quicker and easier, and probably not much more expensive (vs. bulk buying lenses which may never get used)

Firstly, for the diameter 13mm or nominally 1/2" will be fine. 12mm may be OK.
The focal length is very short, so you are looking at aspheric condenser lenses. How short you need is determined by the objective that you are using. 5mm makes sure that you can fill the NA of a high NA, 100x oil immersion objective. 8-10mm focal length gives a lower NA, which will not matter for lower power objectives.
Someone will I hope correct me if I am wrong, but a longer focal length means that you move the illumination up on the dovetail.

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Thanks, very helpful.

Edmund Optics have 13mm ø 7.4mm focal length (NA 0.88) aspheric condenser lenses for £23. MgF2 coating (400-700nm) for an extra £9.

Anyone any ideas if this would work with the “standard” microscope build / delta stage, equipped with a 40X finite-conjugates objective (“160”)?

Would the coating be useful for bright field / reflectance microscopy?

We haven’t announced it because I need to set up a web shop, but OpenFlexure Industries has the nuts/bolts and illumination kits in stock. And can do a limited supply of 3D printed parts. We are still scaling up.

We could sell you the lens quite cheaply. Send me an email at