Haven't tried yet, but someone on the facebook group posted: https://www.amazon.com/gp/product/B01E90JU84/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

https://www.amazon.com/EAONE-Printer-Nozzle-Extruder-Makerbot/dp/B0777KYTJT/ref=sr_1_18?ie=UTF8&qid=1517165577&sr=8-18&keywords=M6%20nozzle

.4 is the size you want, but .3 is apparently very nice for minis. .2 is too small, unless you drastically reduce flow rate and speed. (all per FB group)

ALSO: from the wiki: https://mpminidelta.com/parts/nozzle

https://www.amazon.com/Mercurry-3D-Printer-Extruder-Makerbot/dp/B01E90JU84/ref=sr_1_2?s=industrial&ie=UTF8&qid=1500669351&sr=1-2&keywords=3D-M6+0.2mm would this one work?

All right yall back at it again with a little lesson in 3d printing. An all metal hotend is made with much higher quality and there is no ptfe lining on the inside of the cooling block. The MPSM comes with an E3D v6 hot end (not all metal) however the nozzle does not matter if it is all metal or not.

Nozzles I bought:

https://www.amazon.com/dp/B01E90JU84/ref=cm_sw_r_cp_apa_Rvo6BbHV9F9KV

Edit: I recommend buying the parts from the link you posted due to the tools you get and the nozzles for all the same price