I found an antenna on amclives that looks nearly identical to the one found on an eagle, however it says it's for a rambler, are they the same thing/will it work on an eagle. Here's a link to it: https://www.amclives.com/products/1964-69-amc-american-antenna-replacement-kit-rl-8132
That one isn't anything like the original Eagle (and later AMC) style. It'll work tho; but you'd get the same thing from a $10 universal antenna off of Amazon -- like this one for instance:
https://www.amazon.com/Metra-44-UT30-Universal-Replacement-Antenna/dp/B000K50H3K/ref=sr_1_13?crid=HQGEJ2568VBM&keywords=universal%2Bradio%2Bantenna&qid=1685653472&s=automotive&sprefix=universal%2Bradio%2Bantenna%2Cautomotive%2C148&sr=1-13&th=1
I may have an NOS AMC antenna base somewhere if you don't want to go the universal route - you'd still have to buy a mast for it tho.
I haven't had great luck with some of the generic replacement antennas in recent years, unlike the ones I'd get 10+ years ago. Seems like I couldn't get the claws pushed through the hole far enough to get them to swing into place. I finally got one meant for a classic Mustang from one of the Mustang suppliers and it works great.