I'm just back. Was staying in a hostel so no punting but I did get a few offers on Tinder, Badoo and Mamba. Cheapest was $100 for 1-2 hours. Another offered herself and her friend $300 for an hour. Minsk is not a popular tourist city so I would imagine there's more on offer in Kiev.
I looked here for info before going but there was nothing. There's a long thread on internationalsexguide.nl though if you can make the effort to look for it.