I dont believe the Wren had seat suspension , but can easily be done . Search photos of The Golden Pinto or Duck as the are similar and easy to make . The wren has the shock hole on the tabs where the axle goes thru , You only need a piece of 1-1/4" X 10" piece of flat bar 3/16" thick is good , you'll need exact measurements but approx , you bend 2" 90 degree on each end and drill 3/8 hole for shock bolts and 1/4 holes for the seat mount holes .
The front mount that attaches to the seat is the same just smaller but you'll have to weld a bracket , post and axle tube onto the frame for the front mount , I had to make all new ones for my Birds , it's not difficult !