I got them off ebay, they claim to run cooler than the ceramic ones I have in the other tires. for a 37in tire you need about 10 ounces if memory serves me correctly. You can find a chart online that will give you the exact measurements.
As far as using balancing beads go, it's not a perfect solution but it's a cheap one for larger tires. There will be some vibration until you get the tires spinning to over 45mph (might be different depending on tires) then it smooths out as you pick up speed. The fact that no one nearby wants to work on split rims or have a machine large enough to balance a 37in tire makes this my best bet. Let me know if there's anything specific you want me to address, would be glad to answer.