I have a 2001 Monaco Dynasty, and I have been doing some research on this very topic and will likely replace my air bags next year.
I will pass on some info that I hope will help you. I would assume that you have Firestone air springs similar to what I have on my coach. If you haven't done so already, I would first suggest you go out on the Internet and down the following pfd documents that will be a great help to you.
Firestone airide RV air spring replacement guide.
Firestone air spring maintenance guide.
I have done considerable amount of research on where to purchase these air bags and I found the cheapest price for OEM replacement Firestone air springs were:
SDTruckSpring.com, phone 877-774-6473.
Truckspring.com, phone 800-358-4751.
Depending on what you have under your Executive, the price will likely be somewhere between 169 - $200 each.
To verify the air springs under my Dynasty, I had to contact Monaco because the Firestone part numbers are stamped on top of the top bead plate which can't be seen until you remove the air bag assembly. Then I would physically inspect your air bags to compare their info to what is published in the Firestone literature, as I found that contrary to what Monaco build records indicated, my front and rear air bags are all the same number, W01-358-9376. Monaco techs advised that the rears were a Firestone W01-358-8897, but that was not accurate based upon what was actually installed on my Dynasty.
Hope this info helps and good luck with your new coach, you will love it.