Here are the Hunts Photos sale links to the NiSi Close-up Filter and Focusing Rail. Watch the video about these products. Macro Photo Tips - Beyond 1:1 With NiSi Close up Filter, and Focus Rail (youtube.com)
Here are promo links to 20% off both 77mm and 58mm close up filters.
https://www.huntsphotoandvideo.com/detail_page.cfm?productid=NIRCLOSEUP77II&mfg=Nisi&show=yes&sp=Abgoa
https://www.huntsphotoandvideo.com/detail_page.cfm?productid=NIRCLOSEUP58&mfg=NISI&show=yes&sp=Abgoa
Here is the promo link for the Nisi Focusing Rail.
https://www.huntsphotoandvideo.com/detail_page.cfm?productid=NM180&mfg=NISI&show=yes&sp=m2gRD