Don’t indicate what items in your catalog are out of stock. Accept an order, and let the buyer choose to either
1. have the items they selected that don’t happen to be in stock deleted from their order and have the remaining items shipped right away, or
2. have the order held until all items are in stock and shippable, but give absolutely no indication of when this might be, if ever
and let the only indication that something is not in stock be that nothing shows up at the buyers doorstep.
I mean, I really want to support local purveyors of eclectic material, but I’d also like to know what’s coming before it winds up on my doorstep. At least Amazon explains how long fulfilling an order of the type I made usually takes.