Few options - looks like your hose is inside that piece - you can call Grady and ask for the specific part number used in the manufacture process and then order that directly from a Grady dealer; second option is buying a plastic thru-hull made for this type of application where it's threaded on one end so you'd push that into the existing hole into the electronics box, then it has a plastic threaded lock washer to tighten it down and then you'd just push your hose onto the end and your done or believe they have what's called impact drains (essentially same principal as plastic thru-hull but for smaller hose sizes); can purchase these plastic thru hulls or impact drains from any marine store or online for a few bucks - you just need to know the diameter of your drain hose
See the thread on cup holder drains a few threads down from this one where I replied there - same type of application.
Hope this helps
