I don't know if this helps, but apple IOS firmware links can be found here:

http://osxdaily.com/iphone-ipsw-firmware-downloads/

This list links are to Apple's site. There are similar lists on other sites on the Internet, if this list is inadequate or breaks in the future.

If any phone you get has the version you want, you may still need to have the ipsw file for a restore or other needs.