The soon-to-be-released Primaluce flat/cap looks good
https://www.primalucelab.com/calibration/
I imagine it will be a lot more expensive than the DeepSkyDad offerings, but it will be good to have a high end product with more size options than the Optec Alnitak flip-flat, especially given Gemini Snapcap has been discontinued
http://www.geminitelescope.com/snapc...-tube-ota-cap/