I used to live in a house where the gas shutoff valve for the fireplace was in the living room floor, controlled with a little key. It was the perfect size for a marble to fall in and block it.
I found a metal straw and taped it to the end of my vacuum hand attachment, effectively forcing the suction through the straw. I felt I may have been straining the vacuum a bit, but I was able to pull the marble out easy-peasy.
If you have an attachment that fits in that hole, you’re good. If not, you can use a similar method to this.