Cardone and Dorman make quite a few replacement parts, but I'm not sure they have the pump bracket.
The best choice is to take a picture of your current pump and compare it to what is available at a pick and pull, or find a full service junkyard that will pull it for you. There should be several junkyard GM vehicles that have the part you need, although you might have to buy the entire pump to get the bracket.
What is your location?
Bruce