A cheaper alternative would be not to buy any tanks, their use is very overstated. At the peak of the conflict each side only had a couple of hundred in operation, as compared to around half a million men under arms, that's like one tank per 1,500 men if they were portioned out, which they weren't.
You might get a platoon or two spearheading each brigade attack in the important offensives, but they didn't feature in day-to-day actions, nor were tank-on-tank encounters common; they were only mustered for attacks or counter-attacks and not part of the defensive lines. The respective 'armies of the south' went through the entire war without any at all, as was the case on the Madrid Front once the action shifted to the North after Spring '37.