This is
Ryoko Miyaichi. She's 40+, the owner of a Borgin & Burkes type shady shop in [whatever city you need it to be], in which she enjoys making people regret that they took her for a sweet lady who can't hurt a fly. She has no allegiances, being a business woman first and foremost, and will deal with Death Eaters and Order alike, possibly while offering them baked goods and you know, whatever. Stuff. Things. Edibles. Possibly pie, if you ask nicely.
She also has Yazuka ties through her son. This totally happened because she walked up to the mob boss and told them to leave her baby alone. Why yes, she came in after him. He was... unamused. Me? Finding it hilarious.
Anyway, if our lovely cast needs shady objects, fakety fake fake horcruxes, a cup of tea or someone to judge them wildly, come at her. It'll be fun.