The craft team behind the balls may not do custom Pokemon, but keeping to the original 151 monsters, still gives you quite the selection. Here they talk a bit about their process.
"Each Poke ball is made of a high grade k9 crystal the same material used in high end home decor. The crystal is carved into a 80mm diameter (baseball-size) ball and has fine point 3D laser engraving done to it. Using the latest in 3d engraving technologies we burn the image straight into the crystal. This laser is 5 times more precise than traditional 3D engraving to offer amazing detail and realism to each Pokemon."
I mean, these look beyond stellar. And the best part, they usually make them in about 5 days. Sadly, they are currently sold out but are looking to get a new batch ready for mid-June or July.
So if this is something you'd love to get, be on the look out in a few weeks.