Options to put a pet to sleep

My cat recently got diagnosed with cancer and the vet gave her less than a month. She’s still active but I’m expecting the decline to come pretty quick and with little notice. Has anyone had good experiences with a place to put their pet to sleep on short notice (open nights or weekend)? When the time comes, I’d like to end the pain quickly without having to wait for the vet to open during normal business hours. I’m located in the Montrose area.
The last few days have been difficult to accept. Thanks for your help, Houston.