Look at a Don Hume H710 "First Agent" belt slide. They don't list one specifically for the Shield 45, but the one I've had for my Glock 26 turned out to work fine with the Shield 9, so I'm guessing the Shield 45 would fit too. Inexpensive and readily available.

Don Hume doesn't sell directly, but you can look at their web site to see what their many styles are like. You have to go to an actual vendor to see which designs are available for which guns, though. I start at Gunner's Alley when I'm looking for Hume leather. If they have it in stock you'll get it in a few days.