These types of fungi are notoriously difficult to fruit in articifical culture and even successfully introducing them to a wild or garden habitat requires great expertise. The grassland species are especially troublesome. If you succeeded in fruiting giant puffballs consistently that would be both amazing and lucrative.

I don't know of any commercial suppliers of puffball or earthstar spores, but there are living strains available through various culture collections. How useful live mycelium would be to you depends on what you're actually planning to do. If you want some puffballs in your garden, you could use the culture to create some spawn to introduce to your lawn or to woodchip mulch, depending on the species. I just checked the CBS database, which is in Holland, and they have both earthstar and puffball cultures available. You'd probably want to google a culture collection closer to where you are.

If you're really after spores and a living culture won't do, your best bet is to collect your own from the wild, or to get friendly with other growers on internet forums devoted to the subject.

Here is a link that might be useful: CBS