This is probably not relevant to the original question, but is there a Library in Marleybone, because I know there's one in Krokotopia and Wizard City, but I've looked all around, and could'nt find a place to buy treasure cards...
I think that after you complete the ironworks you should be able to go to an abandoned warehouse and meet with baxter who will sell you pets of members of the o' leary's, like miniature ruffians and bandits. ( Aww they shrink down so fast! )
Suppose they really do not like the idea of having pets, seeing how they themselves are dogs. Also, it is said that they value technology and science over magic. Therefore, is it not a logical conclusion that they might have androids or robots as a "helper" that can be purchased in a shop? Just thinking out loud...
I know where you can get a pet i think. Well anyway i belive that you can get a pixe pet in marlybone i dont have the pet but i have asked someone who does and they said "I am prety sure i got it in marlybone from conterweight west" and i might be wrong so dont get mad at me if you dont get the pet
p.s. the pet gives a card that heals 180 hp
Um actually it's from SMOGGER(in Katz lab) and heals 480.
About the pet shop, my guess is the Marleybonians detest the idea of making pets of any forms of life no matter what they may be. Seeing as cats and dogs are being made pets in other worlds (eg: firecats in wizard city and heckhound in krokotopia).
Also, there is no treasure card shop in Marleybone because they value science and technology over magic. Hence, the presence of airships and cars. Only Arthur Weathersfield in Wizard City can do magic I think (or rather choose to).
Just be lucky that they sell clothing and items that augment our spells. Though I can't guess why they have a wand shop.
The only Marleybone themed pets are the rat and black widow. The black widow is a drop from the black widow boss but it is a rarity to recieve it. I don't know where the rat is dropped but I am sure you can get it somewere.
But then the rats might take offense. XD It would be interesting to have an Ambrose pet... or a mini-me... that would be so awsome to have a mini me because, if it did go this way, what ever spell you use your mini me pet will do it to and do twice the damage? I have a weird imaganation :D