The province drafted in the 30-year-old Australian back on a short-term deal in August and he will make a farewell outing for the club after the final Champions Cup pool match against Wasps on January 21.
Ulster have been working hard to bring in a suitable replacement given that Lealiifano chipped in with 47 points in 15 appearances and Cunningham claims they are close to making the breakthrough.
"We do have plans and we'll be in a position, hopefully, next week to announce a replacement," he said.
"It is a very difficult time of the year to try and get a replacement of quality that is going to make a difference to our squad but I think we've done that."
There are reports that Australia's Quade Cooper and New Zealand's Stephen Donald are the top targets at this moment in time.