> I have not seen any legal authority for the defense getting a search warrant.

I wouldn't expect so, since I proposed creating statutory authority for them as a solution to the problem you described that would seem to be well within the parameters of the Constitution, so that we don't have to sacrifice protection against warrantless searches and seizures by government in order to preserve the rights of defendants to secure evidence for their defense.

I'm quite aware that defense-initiated warrants are not an existing thing.