Aslan Double Up Cuff
This ingenious leather device allows a dildo or plug to be worn by the wearer of any two-strap harness. Slip the two leg straps of the harness through the front and back straps of the cuff, then slide the base of a dildo or plug through the harness leg straps. Pull the leg straps tight, and voila! Your dildo or plug is securely fastened right where you want it.
Top portion of photo shows the cuff alone. Bottom portion of photo shows the cuff in place with a plug on a Jaguar harness (plug and harness are not included).