Can stress/depression or any medication somehow delay hiv seroconversion?

Not known: Only antiretrovirals are known to prevent HIV infection. If your question is about seroconversion per se, i.e. The development of antibodies in the presence of infection, I am not aware of anything that does that.

No studies: It's an interesting question, but i've not found any studies that try to answer it. There are some looking at depression and CD4 count -- depression correlates with reduced CD4 count, and social support with greater CD4 count. Some studies show that depression may suppress immune cell functioning -- so possibly quicker HIV seroconversion, if anything. I have no data to support that, though.