Metric Aircraft Nuts and Bolts

I am building a european glider kit. I am in need of some additional metric
aircraft bolts and nuts, something a grade higher than Home Depot. I have
had little luck finding information on what would be the metric equivalent
of US AN series hardware. I have been unsuccessful in determining what the
nomenclature is.

Can someone provide guidance on what I need to look for and any possible
sources?

Thanks
John Scott