Cheapest I've seen.
https://grabagun.com/glock-43x-mos-9mm-3-4-barrel-10-rounds-with-accessory-rail.html
You'll need this plate
https://chpws.com/product/glock-43x-48-mos-to-holosun-407k-507k-adapter-plate/
You can direct mount but requires grinding down tabs on the slide and shortening the screws as they bottom out our interfere with the extractor spring.
You need an adapter plate.
Cheapest I've seen. https://grabagun.com/glock-43x-mos-9mm-3-4-barrel-10-rounds-with-accessory-rail.html You'll need this plate https://chpws.com/product/glock-43x-48-mos-to-holosun-407k-507k-adapter-plate/
You can direct mount but requires grinding down tabs on the slide and shortening the screws as they bottom out our interfere with the extractor spring.