I do not know if these manufacturers deliver to Europe, but these links are worth looking at if you want to obtain flat strings. This is a post I wrote for a facebook group:
Where to buy scoubidou materials online
I don't know if anyone who sees this has an instagram account, but I have had at least a dozen people on Instagram ask me where I buy my string (please note that these are American style plastic strings, the European scoobi strings appear to be shinier but less dense. In America we call European style scoobi string, s'getti string and they should be on the website links below as well).
I buy all of my string online. These are my favorite 4 but the shipping is HIGH so I order in bulk when I run out.
https://tonercrafts.com/product-category/craftlace/https://pepperell.com/.../plastic.../rexlace-plastic-lacing/https://artcovecrafts.com/.../plastic-craft-lace-lanyard...http://kwikcrafts.com/crafts/category/Rex.html...I also know that Amazon also sells flat string scoobi rolls, but they are like $10 bucks versus $3 bucks on these websites (again the non-Amazon websites have high shipping, but if you buy it in bulk, it's better than amazon's prices):
https://www.amazon.fr/s?k=rexlace&__mk_fr_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=8V0W7AP1F77Q&sprefix=rexlace%2Caps%2C354&ref=nb_sb_noss_1However, one advantage Amazon has it that it has Megalace (I contacted the company and they discontinued the machine that makes the lace six years ago.. If anyone is curious, Megalace is gigantic American-style plastic lace, literally twice the width of regular scoobi string.
I managed to get a good price a year back. Unfortunately, it is only in a 24 pack, has a small amount of colors and can run up to $100 on Amazon:
https://www.amazon.com/Mega-Lace-Bulk-Pack-1200yd/dp/B00MEJTXC6