Try and find a book called 'The Laser Experimenters Handbook' which had
details about how to build many different types of lasers, concentrating on
mixed gas lasers (e.g. CO2). It had plans for getting the tubes blown by a
glassmaker, gas percentage mixes and circuit diagrams of high power power
supplies etc needed to excite the gas. I bought it from a second hand book
store over 10 years ago and it's in storage somewhere but if I remember
correctly it was pretty complete.