A party of monster huntresses descend into an abandoned mine and encounter a grotesque colony of insect creatures that want to mate with them and aphrodisiac mists that make it hard to resist. The entire lifecycle of the monsters are featured in the book, not just the egg-laying.
If you are interested, available on Amazon: https://www.amazon.com/dp/B07ZHLGJV2
Obviously not the exact same cover art :P
I hope this doesn't get me taken down, but here's the link to the full story: https://www.amazon.com/dp/B0BBRT5567/ref=sr_1_1?crid=1TR8MVJ536T4N&keywords=carmen+cade&qid=1661345695&s=digital-text&sprefix=carmen+cade%2Cdigital-text%2C87&sr=1-1
Well, I SAY "egg," but really... https://www.amazon.com/dp/B09YR381NH?psc=1&ref=ppx_yo2ov_dt_b_product_details
The remote really helps make things interesting... ;)
If you want something a bit bigger, in the marble size range, yet still egg shaped you could get some small eggs 3d printed to make a mold from, and then mold them in a silicone of your choice.
something like this could be scaled to the preferred size: https://www.tinkercad.com/things/bkUoJV12kb8-dazzling-bigery-migelo/editv2?sharecode=f1oH55dgZXC_7dpZ20rQkRqE7mraAUjlTPnC4Sz8YKE=