I'm typically a collector of commemorative singles (the strip or block for se-tenants). If I find a stamp especially interesting because of its topic I may also add a plate block, first day cover, souvenir sheet, booklet pane, etc. The FDC's I have I ran across at a bourse or show, in a dealer's shop, or on e-bay, I've never actually gone looking for a particular one.
On April 9, 2021 the USPS will issue in Seattle, WA a booklet with four designs of Espresso Drinks. Coffee is one of my topical interests, though usually the coffee plant on stamps. I would like to add the FDC's for these to my collection.
I notice that the USPS store is offering FDC's (set of 4, $3.96) but the envelopes are not illustrated. Are there private vendors who will offer cachets with first day of issue postmarks for these stamps? Who would one contact? Thank you for any information available.