So, a question. How does one go about purchasing a Bastet at Character Generation?
Step 1: Research your GM's weakness. Often these may revolve around food, for example, home-made toffee.
Step 2: Make a large batch of toffee.
Step 3: Hand GM toffee. Wait 15 minutes, until toffee-induced euphoria sets in.
Step 4: Hand GM character sheet for approval and hope toffee-induced haze prevents him from seeing the Bastet.
As a more serious answer, there are no rules (or prices) for purchasing any technocritters at this time, as fits their rarity. If you want one, it's something best discussed with your GM.