This key guard was designed for the ES 300, but I have confirmed that it works with GS 300 as well. My old plastic key guard broke off in the ignition of my 1998 GS 300 last week. I decided to save money by 3D printing this key guard from Thingiverse.com. I saved myself more than $150 in key replacement costs.
If you would like to download this thing, follow the link below: