I cannot get Tempus Fugit Kina L'Aero d'Or in my home state, either. I found a bottle by accident while buying wine on vacation at a wine shop in Walla Walla, Washington, a thousand miles from my home. You might try Bonal Gentiane-Quina Aperitif or Luxardo Bitter Bianco, both of which I like better than Cocchi Americano for this sort of recipe. And the recipe only has 2 oz of liquid in it as is, making it easy to add a bit more gin to dry it out. The 6:2:2:1 proportions work well, IMHO.
Walla Walla. Interesting vacation destination. Welcome to the Inland Empire! I know of a mountain ridge in north Idaho where you can see all of eastern washington to the Cascades.
It's pretty much on the most direct driving route from Seattle back to Santa Fe, and my sister in Seattle recommended we stop there and visit The Thief wine shop. Turned out to be a great recommendation.
Got hold some Bonal and, yes, it really added herbal depth and bitterness to balance the sugars and richness of the Lillet and apricot brandy. Good stuff!
The Luxardo Bitter Bianco is my favorite bitter aperitif for Vespers, using Ian Fleming's 12:4:1:1 proportions (with equal parts Luxardo and Lillet Blanc). I find the Luxardo makes a brighter, crisper, more martini-like Vesper than does Cocchi Americano or L'Aero d'Or. Slainte!