How to get digging materials in pokemon diamond and where to find it?

Can anyone help me solve this problem, how do i get those digging materials in pokemon diamond?|||Fly to Eterna City and go to the house adjacent (Next to) to the pokemon center. Talk to the old dude and he'll give u an explorer kit. Then he will assign u tasks to do underground.|||You have to visit Eterna City. The Underground Man lives in the house to the right of the Pok茅mon Centre. He'll give you everything you need to get started in Sinnoh Underground. After you recieve the Explorer Kit from him, you can select it from the Key Items section of your bag and go Underground from any outdoor spot you like.|||Just go to Eterna City, and the house right next to the PC, go in there, and there should be an old man, and there you go, hope you have fun down there. it gets boring after awhile though, but have fun|||It's called the Explorer Kit, and you get it in Eterna city. Theres a house by the pokemon center (To the right i think) and inside there will be a guy. talk to him and he will give you an Explorer Kit|||there is a guy in eterna that gives it 2 u... if u take some1's flag, go back to him for a reward