A trekking pole or two would be handy.
Insulation layer for your legs if you don't have it.
I've never seen an umbrella in the mountains. I'm thinking a light weight tarp would serve the same purpose and be a lot more versatile. It wouldn't work for the Mary Poppins routine though. Or just trust your rain gear.
The next step is going through the pile and looking for things you can leave at home.
If your guide is bringing a spotter, I'd ditch that weight, but it is your call. What's that rifle weigh?
