Your contractor should then be telling you which supply houses he/his plumber uses and possibly even giving you the name of there sales person. You can walk-in (appointment is better) and say, "I'm Danno, this is my shorty, we are working with XYZ contactor".
I use
http://martzsupply.com/locations/showroom/
and
https://www.ferguson.com/content/showrooms
For the expenses that are "variable" did he give you an allowance or range? Did he provide any guidance on what may be options within you budget? Because, if not, that "Quote" is BS and expect some major changes once you select your finish materials. Here are two easy examples:
1. Shower tile -6x6 ceramic straight lay vs. marble in a pinwheel pattern set on a diagonal with a glass deco band. They don't cost the same to install. If the install cost is "fixed" problems may arise.
2. Shower Trim - Delta Lahara suite vs. Hansghroe suite with a hand shower and the valve controls on the opposite wall. One rough-in takes about a hour. The other requires about 3 times that plus you'll have to re-drywall the ceiling if the backside of the bathroom is on an exterior wall.
Point being, heads up for "fixed" costs before the finish schedule is complete because sometimes one drives the other. If your contractor is not providing any direction and you wife chooses a furniture style vanity with a vessel sink and a wall mount faucet when your exisiting supply and waste lines are coming through the floor Danno ain't gonna get laid in a month of Sundays once you see the plumbers bill