Maybe this link helps: https://www.researchgate.net/post/Anyone_know_of_a_package_in_R_or_Stata_that_will_estimate_quantile_regression_with_endogenous_regressors_for_data_that_is_purely_cross-sectional

Have followed that thread, but not entirely satisfied with the package I got. But thanks - I will try to work on it

I used the R ri package in a previous article to estimate the effect of a prevention. 

I [just] posted on that other thread:

In R, I have code for a particular estimator within the IV approach:

https://faculty.missouri.edu/~kaplandm/code/ivqr_see.R

which calls functions in

https://faculty.missouri.edu/~kaplandm/code/gmmq.R

You can get other files (including the Journal of Econometrics paper, which discusses some advantages) under "Smoothed estimating equations for instrumental variables quantile regression" at

https://faculty.missouri.edu/~kaplandm