If you are looking for just the hinges these appear to be HP Spare Part Number L23884-001. You should be able to order these directly from HP if they have them in stock or you could do a search on Ebay to see if you can find them there as well. It might also be worth picking up a spare set of screws (L23915-001) in case you’re missing some. That could be another reason the hinges are not as tight as they should be.