Adox A+B comes in two small bottles. You mix a small quantity of each with water to make up the developer solution which you use once. It's a liquid developer like DD-X or HC-110, it just comes as two solutions rather than one. Supposedly separating the components makes it keep better. You mix them before use, they aren't used as separate baths like Diafine.
I bought Diafine in the UK [va MrCad, I think].
FWIW, Adox A+B is a good developer. I find it works particularly well with Fuji Neopan.