Anyone have a contract with a plumber with agreed upon prices?

[Stuart M.]

I have a house that the mainline gets clogged occasionally (it has been scoped, there is nothing wrong with it) but it always seems to be at noon Friday and then by the time you get a call its 6pm, and you're stuck with after-hour rates all weekend, etc.  Does anyone have a plumber that has gives you two agreed upon rates - business hours and after hours to clear a clog - and how did you go about finding them and agreeing to these rates?  There isn't some forum where I can post "hey this is the address, give me two prices, plumbers" and get a response.  And there business usually doesn't work like this - they wait for calls then go respond.  Anyone successful in setting something up in advance?