Here's an easy mod to use your stock turn signal brackets to mount a pair of mini-turn signals...
Loosen the phillips screw and remove the stock signals.
If you can find a pair of turn signals with 8mm threads, you can use the existing metal sleeve that holds the stock turn signals in place. The signals pictured below are K&S signals purchased from Dennis Kirk for about $14. Here's the link:
http://www.denniskirk.com/jsp/product_catalog/Product.jsp;jsessionid=CQZVWXRP...Cut the sleeve in half, and then use a tap to thread it to 8mm.
Screw the turn signals into the sleeve and tighten the phillips head.
If your turn signals don't have 8mm attachments, you can make a custom sleeve. Here's David Finn's description of his turn signal mod he made for his Ryca CS-1:
"I used .625 aluminum round bar and cut a piece 7/8" long which is the length of the inside bore of the clamp. Drilled and tapped 10mm x 1.25, and then cross drilled and tapped 6mm x 1.25 at the side screw location. The 10mm thread fits these turn signals from Hoosier Garage, ordered on Amazon ASIN B0027ZT1Z6. $12.95/pair plus shipping. The side screw locks the signal from turning and matches the stock screw."