Hylomar blue is a non-setting sealant, and might not be the best choice for the application that Al has in mind.
The generic name for most of the sealing goops is RTV (Room Temperature Vulcanising), and covers the cheap and cheerful bath sealant stuff that uses acetic acid as the curing agent, right the way through to two part RTV that is suitable for high vacuum and even space use.
But there are a number of RTV's that seem to be suitable. Just stick with known high quality brands like Loctite, Permtex and Dow Corning, and chose one that is suitable for automotive use - there are ones that seem possibilities that will not break the bank.
Depending on how many you need
http://www.automotioncomponents.co.u...l-screws/p0173 is one supplier of bolts with integral O ring seals. Be prepared for about a fiver each depending on thread size.