I made one out of a $5 bicycle pump at wal-mart and a $2 tire gauge.
Take the gauge apart so that you can hook a piece of hose on the end of the gauge. Then "T" that into the hose on the pump hose and cut off the end of the hose. That is it. There are tons of ways of making them. All you need is pressure on one side and a gauge so you can tell the line pressure.
This one already has a gauge. but is just line mine except I put my gauge on the end of the hose so it is close to the carb.
I used this tire gauge if you wanted to do it that way.