Re: sig sight drift tool.
There are TONS of options for sight pushers.
I have seen the Sig Classic Front/Rear Sight tools sell for as cheap as around $170. If you go through MidwayUSA, you can order one and use a discount code to get another $10-20 off the price depending on the total amount of your order.
Maryland Gunworks makes a Sig-specific tool that runs around $110 or so.
There are also several companies that make universal sight installation tools. I have only used one and I don't recall the mfg, but I am sure that someone will chime in on them. They usually run around $200 I think, but will work on a huge variety of pistols.
If you are just needing a small, one-time adjustment, or you are just looking to install a single set of sights now and not a bunch down the road, your money is better spent on a quality gunsmith who'll do the work with the proper tools and only charge you around $40 or so.