Bing found the following results
HK G36 Bolt Head Complete - US Made - HKPARTS
HK G36/SL8 Bolt Carrier Groups
HK G36, G36K, G36C Bolt Head Complete - German
HK G36 Bolt Head... who makes the best? | HKPRO Forums
HK G36 Bolt Group - Complete New
HK Specialist
G36 Bolt Head, complete | Blue Ridge Supplies
HK G36 Semi-Auto Bolt Group - Complete - GSG9 - HKPARTS
HK Factory Original G36 Complete Full Auto Bolt Group
Heckler & Koch G36 - Wikipedia