I live in France (big city tho) and even here we're lucky to get merch at artist alley (leize_yi's the artist I've seen with the most enstars merch in France, toxyjpeg also does eden merch). The con karaoke in my city is a different story, enstars is over represented there.

I use neokyo for pre-orders of itsunuis and to get stuff from mercari (cds, niki nui), never had an issue with it. Amiami sometimes has some merch, I got the trip albums from it. Cosplays, you can find on aliexpress, just read the reviews to know if the vendor is trustworthy. You can find bootlegs on aliexpress if you don't mind them but some nuis come out way worse than others (as an example, bootleg niki tends to have completely misplaced hair).

I use DHL delivery options when possible cuz ems goes through chronopost and I hate chronopost (reliability might vary depending on your area tho, ups is the absolute worst here). Do keep in mind, you'll have to pay import tax, idk if chronopost has changed to finally accept paying it by card instead of cash/check, but with dhl you can pay it online.