the double stud is not avail seperately

nut is 171 857 026 A, but discontinued. its only an M5 nut with a built in shoulder though, so easy to get. VAG might be able to quote a replacement part number if you give them the old number though.
If you mean the bolts with a bit of threadlock on that are 13mm and go into the slider pins, its 321 615 141 and that works for front & rear. again its deleted though, but VAG should be able to quote you a replacement number. If you go for 443 698 470, thats the part number for 2 of rubber slider pin boots, this will include special slider pin grease and also should come with 2 new bolts also. Yet again this number seems to be deleted, but VAG should be able to give you the replacemnt part number for it.