I didnt book tickets there, but I asked them for some info:
"We have football tours that include transportation and bilingual guide, where you would join a larger group of international fans or just plain tickets. Below are the seating locations (a map of the stadium is attached) and pricing. If you want to make a reservation we will send a Paypal request for 50% that is payable with either a credit card or a Paypal transfer. The other remaining 50% can be paid in cash when you are picked up or when your tickets are delivered to the address of your choice 2-3 days before the game anywhere in Capital Federal, Buenos Aires."
TOUR (mini-bus y guide)
- PLATEA BAJA SAN MARTIN (Lower deck) : $185 USD Very limited availability
- PLATEA ALTA SAN MARTIN (Upper deck) : $160 USD
- PLATEA CABECERA (SIVORI O CENTENARIO, seating behind goal): $135 USD
- POPULAR (Standing, Energetic section)
River Plate: $110 USD
Boca Juniors: $135 USD Sold Out
- PLATEA CABECERA (SIVORI O CENTENARIO, seating behind goal): $110 USD
- PLATEA ALTA SAN MARTIN (Upper deck) : $135 USD
- PLATEA BAJA SAN MARTIN (Lower deck) : $160 USD Very limited availability
Also there's another expats that posted offering a ticket for next Boca/River match if that's what you are looking for.