Philadelphus lewisii.

Here is a link to a nursery in the Gig Harbor area the specializes in native plants.

Here is a link that might be useful: Woodbrook Nursery

You are probably talking about P. coronarius but P. lewisii is prevalent in commerce at this time due to interest in native plantings. You might as well plant the native, unless there is something about P. coronarius you are trying to capture.

If you want to see who had what (among the many participating nurseries) some years back see The Plant Locator - Western Region (2004, Black-Eyed Susans/Timber, Portland).

I like P. lewisii 'Blizzard' because it has dark purple stems that contrast with its profuse flowers, making it more than just a green bush with white flowers.

Sweet Mock Orange, Philadelphus coronarius