Lexar has the 128gb for 49.99. I think this is the cheapest micro SD I have seen https://www.amazon.ca/dp/B012PLSIJ6/Quoting question from earlier in the thread given the Switch's increasingly close release:
or
55.99 for sandisk ultra https://www.amazon.ca/dp/B010Q57S62/
edit: I remember you were also try to buy a power bank. If I were you, I'll hold off until we see how fast a 5V/2.4 or 5V/3A charging to Switch.