Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4873060.
This is a remix of Dog Bowl Water Bottle Carrier, thing number 119689. I added a flat back for stability, a lanyard slot, and belt clip.
The belt clip is from the "KEY-BAK Key Holder, Belt Clip Key Accessory with Split Ring & Steel Belt Clip" available on Amazon (https://www.amazon.com/KEY-BAK-Holder-Accessory-Split-Steel/dp/B081B6L7Y1).
The lanyard is common paracord. Cut a little more than the length you want, fold in half, insert the folded center into the passage in the back of the water bottle carrier, and pull through the top. Hold the 2 cut ends together, side by side, and heat with a lighter until they mushroom and stick to each other. Let cool, and pull into the slot until it locks in place.