Filters

You can attach the female T-2 thread of the C-Mount Adapter to the female 2" SC thread of the 2" Universal flange with our 2" / T-2 (male) Adapter #1508035
https://www.baader-planetarium.com/en/accessories/adapters-imaging-accessories/2-inch-sc-thread/baader-adapter-2%22-(male)--t-2-(male).html

We do have Baader 2" ClickLock M48i clamp (2" filter/photo thread) #2956248 with a female M48-thread.
If you are in the USA, please contact alpineastro.com, our distributor for the USA. You can also use our dealer locator at https://www.baader-planetarium.com/en/storelocator

Yes, you will need our Diamond Steeltrack M68 Adapter (#2957206):
https://www.baader-planetarium.com/en/diamond-steeltrack-m68-adapter.html

Please note that the K-Line-filter is only intended for photography, not for visual use, as the K-line is well in the UV.

You can't combine K-Line and Solar continuum, as one filter only lets green light pass, and the other one only deepest blue.

You can replace the Solar Continuum with the K-Line-filter, but the image will probably still be too dark - and it will almost certainly be much too bright if you remove the ND3-filter, too. This depends on the sensitivity of your camera and on the f/ratio of the telescope, so we can't say which filter will be the right one.

The photographic version of the Herschel wedge contains three 2" ND-filters. If you do not have the photo-version of the Herschel, you can also buy them seperately at
https://www.baader-planetarium.com/en/filters/polarizer-neutral-density/baader-neutral-density-filter-(nd-1.8-t1.5).html
As the K-Line-filter is only 1.25", you can also buy only the 1,25"-filters for photography.

You may need more than one filter, if you use e.g. a Barlow lens for higher magnifications - then you need a stronger filter like ND1.8 for lower magnifications and e.g. ND0.9 or even N.0.6 for those times when the seeing permits highest magnifications.

Unfortunately, exporting it to the USA commercially is almost impossible. We'd recommend to contact our distributor in the US, www.alpineastro.com, for cleaning fluids available in the USA.