Were I a designer, I would avoid you like the plague. If my previous work and reputation had no value to you, we aren't right for each other. That "always get 3 bids" crap is long over with.

Like dating, you need to woo the designer you want. Something like "Hello, Ms. Designer. I saw the work you did for Ms.X and was very impressed. I hope we can get together soon."

Good professionals aren't taking any communication from anyone else; too busy and at capicity.

I think they'd charge you their normal hourly fee to come up with a proposal for your space

You can totally ask them to make proposals as long as you are willing to pay their rates! Ask what their fee structures are and take them into consideration when deciding whom to solicit proposals from.

That you! Good advice.