There are a ton of "tips" on the internet, such as http:[remove this]//www.guntechtips.com/bluing/bluing.htm
Short version: I guess if you really, really want it, you'll need to learn to do this yourself ... or find someone crazy enough to try.
The 2 oz tube of Birchwood Casey "Permablue" I have, when used with an ammonia-based finish remover (first) and really hot parts (just becoming uncomfortable to hold) appears to do reasonable deep blue color. I'm not sure I'd want to do a whole pistol or revolver with the stuff, and durability may be questionable, but the results are pretty. Sorry, photo skillz are lacking, as are many others:
(Restricted "factory" SIG P225 barrel -- modified by me)
You can see the blue sheen on the barrel. I haven't fired that pistol yet to see how the barrel finish holds up, it got several cycles of cleaning, boiling water, blue, polish, repeat... this is the only do-it-yourself product I've seen which isn't a coating (Blue Wonder) and gets that deep blue color.
I have no idea how old the Birchwood Casey tube of blue goo is. 5 years at least. Formulas change, products become better or worse, and of course the steel also decides a great deal of the finish color. There are a LOT of threads about bluing though.
If it were my model 27 and I was hell-bent to get the right color on it, I'd learn how to do proper boiled bluing (on stuff that doesn't count) and test on a few lesser pieces. Then I'd do a great job and come back here and brag about the results. A lot of effort for a little bragging though. As far as paying someone to do it, the Canadian way, you've heard the Pros: there ain't no such thing.
Cheaper to find a minty one, sell the one you have as a "shooter", and move on. They are wonderful guns, I have the model 28 with the lesser finish and a 4" prohib barrel, and it is the most accurate handgun I have ever fired.