The 23-year-old frontrunner had been on a short-term deal at Second Division Cambridge before being released in the summer, but Cambridge's loss is a big gain for the Third Division side, according to Turner.
"In all honesty I can't believe we have got him," Turner said.
"I spoke to Danny Wilson when he was at Wednesday and tried to get him on loan a few times but for one reason or another it never happened.
"I even tried again before he signed for Cambridge but it did not come off. But now we finally have him here.
"Richie is a Kevin Henderson-type player in that he's a hard-worker.
"He's also a left-footer which gives us balance up-front. He can score goals and has done it at the highest level and I feel he will be a real force in the Third Division."
Meanwhile Turner wished the departing Tommy Miller all the best following his switch to Premiership side Ipswich Town.
"George Burley has seen in him what we have known for a long time ‚Çô that he is an outstanding talent.
"We have been saying for a long time that Tommy is the best scoring midfielder outside of the Premier League. Now he is there we want to see him fulfil his potential.
"Of course he will have to work hard to get his chance but I am sure George Burley would not have taken him there to sit in the reserves."
