The FAT wrenches are about $40-$50 on ebay.
I use a regular click style torque wrench with a socket on it that fits my bits when I mount scopes or mess with forearm screws.
Check the pittsburg tools torque wrenches from Harbor freight. They can be had for less than $20 and hold up great. I have had a complete set of HF torque wrenches for 5 years and they get used alot...I drive a Jeep and always have to work on it. My first torque wrench was a crapsman and it fell apart the first time I used it. It was all plastic. The ones from HF are all metal and have lifetime warranty.