Lenovo ThinkPad Port Replicator Series 3 with USB 3.0 - Port replicator - for ThinkPad L420; L430; L520; L530; T400s; T410; T410i; T410s; T410si; T420; T420i; T420s - Walmart.com
I found a ThinkPad T420s at a swap meet and a dock for it in the store whose parking lot was hosting it. An $80 score! : r/thinkpad
Lenovo T420 Docking Station for sale | eBay
Lenovo 4338 T410 T510 T520 T420 Docking Station USB 2.0 with Key | | AMSO
Lenovo Docking Station Dock THINKPAD T420 T420s T510 T510i T520 X220 Port | eBay