Millet, there are several citrus species/varieties that come true to seed (or come very close to being true to seed), even though they are not polyembryonic, and may not be exact clones of their parents. Many heirloom lemons tend to come true to seed, as well as wild pomelos. To some extent it may depend on your definition of "true to seed", it doesn't have to be an exact genetic clone to share nearly all of its fruit traits in common with its parent. In some cases both lines of a parent's chromosome pair may be identical (from inbreeding), so the offspring may end up having the same DNA as the parent, even if the seed it grew from was zygotic. In general, sour citrus varieties tend to be more likely to come "true to seed" or produce offspring very close in phenotype to the parent fruit.
Take a wild citron, switch around a few genes, and the fruit will still be pretty much the same, in most cases. It might not be a clone, but it's still pretty much the same type of citron, overall.
I'm not sure about some of the specific named pomelo varieties with unique traits, but many of the general pomelo types can usually be propagated from seed.
To answer the original poster, unfortunately pomelo is not that common in the U.S. so it can be very difficult to find fresh seeds. If you do find pomelo seeds, they are almost certainly going to be the variety 'Chandler'.
This variety was a hybrid between "Siamese Pink" and Siamese Sweet, a particularly sweet but flavorless pomelo (doesn't have a huge amount of fragrance either), so a seedling from Chandler might turn out to produce insipid fruits.
But I could be wrong, I don't really know for sure.