Autozone has the Dorman 15 in. Universal Ground Strap:

Silver/Grey
Conductor Material: Copper
Conductors: 1
Corrosion Resistant: No
Gauge: 10
Length (In): 15
Number Of Conductors: 2
Stranded Or Solid: Stranded

Would a couple of these work for grounding the transmission?

Seems like 2 gauge would be overkill ...