Thanks to the Internet Archive, I was able to download an 1862 copy of Godey's Lady's Magazine, which has several pictures of Garibaldi shirts, I've complied them below, for your viewing pleasure.
|The Garibaldi Shirt - Images complied from Godey's 1862 edition|
As to drafting a Garibaldi shirt pattern, I'm playing the mad scientist and my plan is to make my own 'Frankenstein-Garibaldi' by cobbling pieces from various patterns I've bought in op-shops.
The Bishop-style sleeves in the two Vogue patterns on the left look about right to me, and the Very Easy Vogue has the drop-shoulder I'll need. The Simplicity pattern has a collar that I think will work...
[Cue the lightening and the maniacal laughter]