They are usually soldered in place on the nozzle adapter and can sometimes be shortened and resoldered. They are not currently reproduced or available anywhere. You can sometimes find one on ebay. There are a lot of gas nozzle bodies out there that are missing spouts and 99% will never find one.
If the nozzle is something special to you, it may be best to search for another example on ebay or facebook and rob the newly purchased nozzle of its spout.
I have a lot of nozzles and I know another fellow that has a lot of them too.