The 19-year-old will remain with the Bully Wee until January 13, dropping down from Irn-Bru First Division side Airdrie United.
Duffy said: "It's no secret that we've been looking to add to our options in central defence. Ricki is left sided too which is another positive.
"I went to see Airdrie play last Monday and I was impressed with his performance.
"Although he is still a young lad, he is a big strong player."