I'm guessing all the cheap Leopard 2 are off the market?
BTW, a while back Norinco did offered the option of equipping 120mm main gun for the VT4, and they should still have plenty of surplus Type 89 SPATG 120mm 50-cal barrels around. The bigger issue will be reconfigure the internal for the large unitary ammo. I would expect the back of the turret will get chop off to install an enlarged autoloader from the VT5/Type 15 lightweight MBT.
Also, paying for it will not be a problem as Brazil had just agree to trade with China in RMB.