@tsalo we have a single dataset that is complex and multi-echo but not released yet.
In the complex-valued datasets you mentioned, most should be already available through CONP for the subset of subjects that ask their data to be pushed there.
So you should already be able to
datalad install -s https://github.com/courtois-neuromod/retinotopy.git
cd retinotopy
git checkout dev
datalad get -J8 sub-0[135]/ses-*/{func,fmap}