I'm bored, apparently, so I did some searching around.

This one is slightly similar, a little smaller at 19" L, 15" W, and 15.50" H. All for under $25! IRIS Large Split-Hood Litter Box with Scoop and Grate, Blue

This one is a little closer to your dimensions at 22x18x18.5, still slightly smaller. Available on Amazon prime for <24$. Petmate 22026 Jumbo Hooded Litter Pan,Assorted Colors

This delightful little box is closer to your specified dimensions at 19.19 x 23.71 x 16.17. Not found on Amazon but you'll enjoy a retractable lid for easy cleaning that also deters dogs! $34.99

I've looked far and wide but I can't seem to find your specific litter box. I hope you find a suitable replacement!

Also please don't tell my girlfriend how I spent my afternoon.

Awwww shucks /u/turtledave, you're a swell fella. Thank you!