In vitro enzyme production
New England Biolabs, which has an excellent reputation for well-tested, well-documented, and robust products, has a line of protein expression and purification products that I'd definitely take a look at. I've used the pMAL system for expression of fusion proteins in E. coli, and the PURExpress system looks just like what you're looking for. I have a personal (but not financial) connection with them, and I can vouch for their quality and technical support.

Pierce/Thermo is generally a good place to look when dealing with protein stuff. I've had good results with lots of their stuff, but I haven't done in vitro expression in ages, so I can't remember what I used. (BTW, I have no connection with them, I just tend to like their products.)

As Alan Boyd mentioned, lots of companies like Life Technologies, Promega, Qiagen, and Sigma have in vitro expression kits. Which one you pick will ultimately be influenced by what exactly you need your protein to do, the desired scale of expression, the type of tag(s) you want to put on it, what equipment and expertise you have in your lab, and how much time and money you want to invest.