When I used to work at a bike shop, we had a term for some customers, snot ball rollers. They came in during the peak rush on a weekend and took up an inordinate time of a salespersons for some tiny obscure part, an off-size spoke,etc., which we always had. Of course, after getting exactly what he wanted, he went throught the roof over the cost.

If you don't want to pay for the convenience of getting piddling parts immediately, go online and wait a couple of weeks.