Full zip GTX shell pant

What options exist for a full side zip gore shell pant? Thinking for emergency oh shit storms while winter climbing. Mammut used to make a pair that was incredibly light but seem to be gone now. Arc has the Alpha and Beta pant (what's the difference?) but $$$. Montbell has a pair but almost triple the weight of Arc. Again as there are an emergency pant would like them to be pretty light. Any other good options I am missing? 

Thanks!

REI has their own brand which is pretty similar to the Marmot precip. I have both and they're reasonably light and durable. 

I’ve used OR Acentshell in a jacket and it works great. Waterproof and light weight. These pants are side zip to the hip so you can still get them on over whatever kit you have on. And they don’t break the bank. https://www.outdoorresearch.com/products/mens-motive-ascentshell-pants-279987?variant=45646537359681

Mountain equipment tupilak are the best I have ever used for climbing but they are pricy and hard to get in the USA

Montbell has fullzip three layer monolithic pu “THUNDER PASS FULL ZIP PANTS”. 10oz and $100 shipped from their Japanese store.

IME ascentshell is not waterproof enough for hardshell pants— it wets through with direct contact with wet surfaces (eg sitting/kneeling on wet snow).