I made a 2 string coursed canjo earlier this year. I used two B strings (.013) from an electric guitar and it seems to work pretty well. I actually wrote a blog post about it here: https://cigarboxnation.com/profiles/blogs/the-accidental-canjo
That looks nice! And I haven't yet done an amplified canjo - some day.
But that looks like a 2-string canjo, rather than a double-course version, where the strings are close enough that they'd be treated as a single string when playing...
I got something similar to this in mind for some future builds. I've done what you've thought of with the 2 e strings before and it works for a 2 string diddley but not courses. have a look at some sets of 12 strings for electric and acoustic guitars and see what gauges will work for courses. Also how many strings do you want on your Canjo?