You don't need a fancy set. I bought 3 punches from Menards (home center like Lowes or Home Depot): 1/16, 3/32, and 1/8". I also used a small flat-blade screwdriver, and a small tack hammer.
Total cost? About $10. And you don't have to pay shipping.
If you're planning on removing the extractor in a detailed cleaning of the slide, you'll also want an L-shaped pick to pry it out of the slot. But that's really all you need.
I just installed a Powder River trigger kit in my XD45 and all I needed was the three punches, tack hammer, and small screwdriver.