If you are not in a major rush, you can attend the ROMPEX show in May up in Denver. There should be multiple dealers there with discount postage and you can pick and choose to your heart's content.
See:
http://www.rockymountainstampshow.com/Another option might be to contact or visit the Rocky Mountain Philatelic Library, again see:
https://www.rmpldenver.org/I would not be surprised if they also had discount postage available, and you would be supporting a good cause.