8020 frame is 5mm instead of normal 6mm, see post here about issues. Think I’m going to get it from Misumi. Believe the total cost is around $95.00 but I haven’t double checked my figures.
The first link above also has the hidden corner connections from aliexpress that should fit the normal frame.
Also a good place for the metric nuts, bolts, etc is boltdepot.com that way you dont have to buy bags of un-needed parts. Can purchase by the individual component. I think for all the metric stuff they have available is only costing around $20.00
That’s about as far as I’ve gotten, I’m still in the process of printing parts and putting together a spreadsheet of where to get remainder.