I would suggest the Odontodactylus Havanensis mantis, it’s like a baby peacock!
As for where to get them, I never bought off the internet. If you live near socal I can point you in the right direction.
10g tank is small for really any mantis, so getting one of the smaller mantis is idle. Even the Odontodactylus Havanensis says it has a minimum tank size of 20g.
I would also suggest to place a piece of acrylic on the bottom of the tank. 10g tank is going to be thin glass. They don’t usually punch the walls of the tank, they break glass when trying to dig, and it usually happens when they hit in the same spot over and over again.