Hi Mike and welcome. One of the best Red/Green Dot Optics for a direct slide mount is the Holosun 407K X2 or 507K X2 depending on which reticle you prefer : budsgunshop.com/product_info.php/products_id/137910/holosun+he407k-gr-x2+reflex+sght+2moa+dot ---------------------------------------------------- budsgunshop.com/product_info.php/products_id/128941/holosun+he+507c-x2+1x+multi-reticle+green+black+hardcoat+anodized ----------- Cheers, stay safe and enjoy! This guide will help you decide : https://freedomgorilla.com/collections/springfield-xd-s-mod-2-osp-optics-adapter-plates

The Springfield XD-S Mod 2 OSP is an RMSc footprint. This means there are four recoil lugs. The optics we recommend are the the Holosun 407K, 507K.
On the Springfield page, they show one with a Crimson Trace optic included.
springfield-armory.com/xd-series-handguns/xd-s-mod-2-osp-handguns/xd-s-mod-2-osp-4-single-stack-9mm-handgun-w-crimson-trace-red-dot/

I put a holosun 407k on mine with excellent results. Its a great sight for sub compacts