I had to create a completely missing Atari 600XL keyboard key. The key is a variant of discontinued Cherry M8. For the key cap I used Parametric Cherry MX model. The spring is from this button. It's not perfect but it kind of works...

Here are keycaps parameters:

[ // 13 - Atari 600XL Profile 18.16, // Bottom Key Width 18.16, // Bottom Key Height 5.40, // Top Key Width Difference 5.3 4.60, // Top Key Height Difference 4.7 8.2, // total Depth 8.2 2, // Top Tilt 3 1.8, // Top Skew //Dish Profile 3, // Dish Type 0, // Dish Depth 0, // Dish Skew X 0 // DIsh Skew Y ],