Unfortunately there practically aren’t, CT these days is done only with iodine contrast*.
Other options might be MRA/MRV with gadolinium-based contrast which might be even more toxic, especially in the long term, but some people tolerate it better.
There is some good amount of information in the FAQ about the imaging options and will provide you with elaborate answer.
*There are very rare cases when GBCA contrast used to be used in the past with CT scans, though this is not the mainstream practice and doesn’t work the same way as iodine-based contrast media.