There are a couple of threads on MFF with agency girls, hard to dig them out though. Diva do have a couples service page
External Link/Members Only from that list, I've seen Marika, who has mixed reviews on here, Astrid who is a bit rough, but enthusiastic, Frieda, good but over 30, Aquamarine and Babi who were both great, those two would be my choices. Adagio and Runa also both have pretty good reviews on here.
I'd recommend asking the agency for a recommendation as they get the direct feedback and then checking on here for any red flags.