Here are options:

Aqua-Rite In-Ground Chlorine Generator - up to 40K -- Amazon, $1060 + $0 shipping

Aqua Rite In-Ground Chlorine Generator up to 40,000 -- Amazon, $950 + $12 shipping

Goldline Controls Aqua Rite Salt Chlorination -- A1PoolParts, $1059 + $0 shipping

For comparison, here's an AutoPilot 40K pool unit:
AutoPilot 110/220-Volt Digital Chlorine Generator with Super Cell -- Amazon, $1454 + $0 shipping