You most likely will have better luck on ebay for both of those than here.

As you mentioned, the Starship Enterprise is almost always available on ebay, often for as little as $35. That kit was most likely the most over-produced kit ever bagged by Estes. Supply FAR outweighed the demand. The 3 major Star Wars kits (non-Maxi 18mm power X-Wing, TIE Fighter, and 4" diameter R2D2) come close in OVER-production.

The K-27 Honest John is FAR rarer, but does pop up on ebay from time-to-time; you may find someone on this forum that has one in 'builder' condition they are willing to let go of though. That kit BY FAR is the best HJ that Estes ever produced. The Maxi-Brute kit is FAR underpowered with a D12, and all the other plastic-nose versions they have produced in numerous sizes after the K-27 are DUDS in my book.

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