Fake quail eggs for nestbox?

[AOrchard]

What do you use for fake quail eggs? Wanting a thrift/found object ideally. I use golfballs with my chickens to great success. 3 of my 4 quail hens will only reliably use the nestbox if there are already other eggs in it, so I need something I can leave in there. Thanks!

 

[Nabiki]

I bought these to discourage an egg eater.
https://www.amazon.com/gp/product/B01MRVA9S2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1