Shop local plumbing supply retailers so you will have a good idea of what is available immediately. Visiting at least three retailers will provide much needed information, such as the brands that are available, the finishes that are available in those brands and the styles that are available by brand and finish.
Ask the retailers if they offer a special order program to customers in their plumbing fixture line. The retailers that do may have a significant set of options for you to look at in their special order catalogs. The down side of special order plumbing fixtures is that they will be more expensive to special order.
Select the styles and the finishes that you like based on the information gathered in step 1 and 2. Plumbing fixtures are usually available in style groups where the shower fixtures, the lavatory fixture and the toilet hardware will match in style and finish.
Identify which fixtures you need to finish your project. Every project is different and will present a different set of needs. Ask your plumbing contractor which fixtures will be required to finish your project and make a note so you will not forget while shopping.
Note the prices of the plumbing fixtures that you like while you are shopping---both in-stock and special order models, if any. If the fixtures you like are sold separately, add the prices together to calculate the cost. Those fixtures that are available as a set and that are priced the same way have been added together for you and need no further calculations.