Which spherical object used in sports is closest in size to an average pomelo?

Pomelos are similar to grapefruit and are very large usually ranging from 6 to 10 inches in diameter! Below are the different size balls that fall in that range measured in inches...

Rhythmic gymnastics ball 7.1 to 7.9
Team Handball 7.3 to 7.5
Volleyball 8.15 to 8.39
Bowling 8.500 to 8.595
Football (Soccer) 8.5 to 8.8
Korfball 8.5 to 8.8
Water polo 8.5 to 8.9 (used for male adults)
Netball 8.9
Basketball 9.4

https://www.topendsports.com/resources/equipment/ball-size.htm

The pomelo tree may be 5-15 meters (16-50 feet) tall, possibly with a crooked trunk 10-30 centimeters (4-12 inches) thick, and low-hanging, irregular branches. Their leaf petioles are distinctly winged, with alternate, ovate or elliptic shapes 5-20 cm (2-8 in) long, with a leathery, dull green upper layer, and hairy under-leaf. The flowers - single or in clusters - are fragrant and yellow-white in color.

The fruit is large, 15-25 cm (6-10 in) in diameter, usually weighing 1-2 kilograms (2-4 pounds). It has a thicker rind than a grapefruit, and is divided into 11 to 18 segments. The flesh tastes like mild grapefruit, with a little of its common bitterness (the grapefruit is a hybrid of the pomelo and the orange). The enveloping membranes around the segments are chewy and bitter, considered inedible, and usually discarded. There are at least sixty varieties. The fruit generally contains a few, relatively large seeds, but some varieties have numerous seeds.

https://en.wikipedia.org/wiki/Pomelo