Wilderness Exchange is within walking distance of Union and they require you leave a bag with them when you go into the store, they may be willing to stash your bag for a few hours. No guarantee on that, but an option if you can't find anything else. They are only open 10am-6pm on Sundays, so you may have to wait around a bit or pick it up early depending on when you get there and will be leaving.
Material: steel is the traditional material; but wood, plastic, or laminate are sometimes used. Plastic or laminate lockers are sometimes advocated in environments, such as near swimming pools, where moisture accumulation may cause steel lockers to rust over time. They can also be used in external applications where internal space is not available.
Attractive, functional, durable, and easy to install! Maximize your space and keep students organized with I.D. Systems lockers. The Lockers 1 Tier 3 Wide Employee Locker are built to withstand the daily wear and tear and are guaranteed free of defects in materials and workmanship for up to five years. This triple wide locker with a shelf in each locker provides adequate space for storing personal belongings and school supplies. Each solid door opens to 180-degrees to keep doors from swinging...
Stored my luggage for several hours at Lugden. Great location just across the street from Union Station. Spoke with the owner and he said he owns the parking spot so they are always there during the day. Prices were reasonable and I felt comfortable storing my bags there while I explored Denver. The owner was nice and gave me coupons for some local businesses.
Centrally located between Downtown Denver and the D.T.C., Colorado Center was designed to be the central location for everything in your life. From a high-quality office environment to great restaurant and entertainment options, Colorado Center is a premier transit oriented development with three existing Class A Office Buildings. Tower III will complete the office component of the project, along with future Residential and additional Retail.

Lockers Denver