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 