Here are a couple quick ones I made. Both are 10mm tall. Included are the .step files so you can chop them up as you please!
Triplelinks 10mm Tunnel Riser.step (71.5 KB)
Triplelinks 10mm Tunnel Riser.stl (270.9 KB)
Triplelinks 10mm Y Riser.step (96.2 KB)
Triplelinks 10mm Y Riser.stl (572.4 KB)