I had this same problem 3 weeks ago. Did my brakes, and the last slide I tried to remove was frozen in. No combination of PB Blaster, hammer, wrench, vice grips, or bench vise could loosen it.
I needed one ASAP, and the stealership had one in stock for $75, plus $4 for a new slide (bracket doesn't come with any). The slide doesn't even come with a boot; luckily I was able to reuse my old one.
I just happen to have a spare bracket laying around, even comes with 1 slide

Sell it to you cheap!