Had this many times before on here, you need: 2 x Stainless Steel Socket Cap Bolt M6 x (1.00mm) x 20mm 2 x Stainless Steel Flat Washer M6 15mm o/d 2 x Aluminium Collar M6 Thread 8.5mm o/d 5mm length 2 x Aluminium Collar M6 Thread 8.5mm o/d 3mm length All from Probolt (stolen from a post by RRoss) http://1000rr.co.uk/threads/seat-securing-bolts-oem.30670/#post-421472
Just use copper slip or moly grease! They won't seize then, make sure you use the right screwdriver as that is part of the cause of rounding them off, mine are 9 years old and never had a problem