For the valve here is a cheaper option that is rated for a much higher pressure.
http://www.airbagit.com/Brass-Air-Va...irvalve-02.htm they also offer mounting brackets for them as well as rebuild kits. That is the one we used on a t-shirt cannon on my former team and I can verify its response time is very quick because we were able to control the distance of the shot by how long the valve opening pulse was.