It can be awkward that there's no single canon database, but there's still resources for it:

• http://klingonska.org/canon/ has everything up till around 2012, it's searchable and if you have a copy of TKD on hand you can read the transcripts of the published books. It's probably the closest thing to what you want, except for missing the last five years.
  
• https://www.qephom.de/e/message_from_maltz.html has messages to Lieven. It's not searchable (well, you can try a site-specific google search) but it's brief enough to skim through.
• boQwI' has canon for many words, if you have an Android phone or feel like installing it on Chrome. http://www.klingonwiki.net/ also has some canon resources, especially links to qep'a' words, movie dialogue, and the like.
• If you keep your messages from KLI in an email folder, you can search that, since most canon ends up here.

It can be helpful to just browse through the canon, like rereading qep'a' notes or the info on klingonska.org, not to look up a specific word but just to read what's there. After a while, you'll start to get a feel for which sources have canon for which words, and also get a feel for which words don't have canon associated with them.