I'd think it wouldn't be that difficult.  Script to start at 0 and add 1, echoing to a file, until you hit 99,999.  Each time, check value, and if below 10, 100, 1000, 10000, prepend missing 0's.  I don't have time to write such, right now, but wouldn't think it too hard.

HTH

I take it you are attacking an organization where you expect this type of password to be in use?

When pen testing an organization, I try to find the company's new employee security orientation and get the examples of what a strong password looks like.  Then I generate some permutations of those and go to town.  Amazing how many people use them even though it specifically says not to in the documentation.