I’m unfamiliar with Philadelphia, but my favorite place to get dried mushrooms is a Polish market. Ask for “borowiki” which are Boletus edulis, same as porcini but more fragrant because of the soil they grow in. They are insanely popular among Poles, so they tend to be very fresh. Philadelphia has a relatively large Polish community, so I’m sure there are several markets in the area.
My aunt, who lives far from any Polish market, has been pleased with these from Amazon.
https://www.amazon.com/Porcini-Mushrooms-Premium-Borowik-Szlashetny/dp/B0783NMFPZ
