Wondering if anyone has found extensions of how to utilize a 1/2" tool on ER-16 collet?
If the ½" Shank fits into the next larger size that of an ER16 then you should be able to find them on AliE. It’s how I managed to get an M10 Threading Endmill with an 8mm Shaft to work on an ER11 ( usually only capable of receiving Shafts up to 7mm in Diameter ) one with surprisingly good results 
( though one might argue for my bar to pretty low 
).
Just search for the Collet you have and the next larger Size + Adapter and you should be golden 
Be aware though that these Adapters will cause like 45mm of additional Stickout 
Another thing to keep in mind is rigidity. An extension or adapter will work, but the extra stickout can introduce more deflection, especially if you’re taking heavier cuts. If possible, I’d keep the tool projection as short as you can and only use an adapter when there’s no better option.