Hi,
Just from my history, I was able to get into a couple of master's program in I/O with no research experience at all so you are better off than me in that regard. If I were you I would look to take more stat heavy courses (if you haven't already) to show schools you have a strong background in it to offset lack of I/0 courses.
Going straight from undergraduate to PHD is a tough road so if you have the financial ability, getting a masters won't be a bad idea. Gives you more ideas on if you really want to study I/O psych full time or not.
Good luck!