How can I get an update on my National Guard bonus?

With the limited amount of information you've given, I doubt anyone here could help you. You didn't mention much more than was is in your question and the tags on your post (what's your bonus, who is giving you status, etc.)

However, taking a shot in the dark it could take up to four months between putting the information in GIMS (Army National Guard Incentive Management System), having it verified, going to NGB (who may or may not have to verify as well), before it makes it to DFAS ... and it all depends on how fast the speed of bureaucracy is and assuming that there aren't any errors that kick it back down the chain.

Check with your S1. Remember the squeaky wheel gets the grease.

Sit down with your Readiness NCO at your unit and say, "Show me in GIMS exactly where my bonus is right now".
They should be able to show you the actions history on your case, and that shows the date each step was completed and what step it is pending at since that last date.
I used to do this every month.

If your Readiness NCO does not have access to GIMS, (a required access for the job because it's a unit pay function) then your Readiness NCO is likely the step that your bonus is stuck at.
If that is the case, you need to talk to your CO, because your RNCO's lack of required access is resulting in delayed pay.