There is a book and video by Paul C. N. Lee entitled (exact spelling):

The Kiuten-irimi-tenkan-jutsu of Aikido
(Elements of Chinese Kungfu in Aikido)

In it there are solo irimi-tenkan movements presented in a slow Tai Chi-style style. It might be similar to what you describe. However, I've never seen this material on general sale anywhere. I was fortunate to pick up my copies when Lee sensei was a guest at our dojo several years ago.