The command sivqr (smoothed instrumental variables quantile regression) is now available on SSC, thanks to Kit Baum. (Very briefly: it's like a combination of ivregress and qreg.) Details are at
https://kaplandm.github.io/#sivqr
including a paper describing the command (revision under review at Stata Journal).

If you have questions, please email me or mention me (@David Kaplan) in your Statalist post (so I get notified); I'm happy to try to help. =)

Dave