There are some shops and web-stores which have manga-tools in the world nowadays. Kinokuniya, Animate, for instance. Some of the tools are available at such place, a stationery shop or an art shop.

Paper
Drafting Paper. Or quality paper. Actually, anything will be OK, but the surface should be smooth. Maybe you can buy guided(blue line) or non-guided manga-paper at some manga-shops. Basically, there are 2 kinds -- 110kg and 135kg weight paper. I use 135kg's one.(110 is too thin for me)
Deleter comic manuscript paper/type-C

Be careful, if the measure of your country isn't "meter", the guide is useless. When I drew "Nozomi", I made the guide with blue pencil by myself. Make sure the mechanical guide to publishers.