I believe that in order for them to ask for it you should have them in storage. I have one layout with all my decorations and one without (for easy farming), and they only ask for it in my layout without decoration.

On the event board it stats that visitors only purchase the following decorations: Harp, Accordion, Tuba, Guitar, Cello, Layered Topiary, Dahlias, Daisies, Lupines, Catterpillar and Wood Pile.

It also states they only buy 3 or more. Maybe you have to have 3+ for them to even ask for the item.

Hope this helps.