Good idea Chad. Tis what'll I'll do...keep a little stocker and eat that for dinner...saves some fish in the process with not "pumping" using the right technique on the skill of the pumper & keeping 1 little guy is just fine. Catching ain't a problem in my camp.
I think the biggest mistakes made when pumping fish are inserting the pump too far down the throat, pumping fish that are too small and handling the fish by hand out of the water to perform the pump.
The pump does not need to go very far down the throat to be effective as most of the feed found in the stomach will have already been partially digested rendering it useless for observation.
I insert the pump very carefully just beyond the back of the throat not more than a half an inch to pull the last meal eaten. I am careful not to hit the gills, keep the fish under water in a large rubber coated release net, never pump water down the throat and am done in a matter of seconds.
I don't have the ability to track fish for hours to check the mortality rate after release, but I can honestly say I have never seen a fish go "belly up" after using it on many many trout.
The findings can prove invaluable if you know what to do with the information. Seeing a chromie lit up as well as other physical characteristics of the chironomids found in our lakes really opened my eyes for tying better representations.
To answer the original question of where to buy one, I think Puget Sound Fly shop has them in stock.
It should also be noted that the type of fishing you do should dictate when a pump is used. Because of the size limitations of the pump, you will not see anything but small insects -mostly chironomids if you fish lakes. Snails, minnows, crawfish and other large feed will not show up in a pump so think about what flies you will be fishing with and whether it makes sense to pump a fish before doing it.
Amen about not pushing the pump too far down. But pumps do have a place, even if you are already catching fish. Here's an example.
A friend and I were fishing Rocky Ford a few years back and catching fish only sporadically, primarily on small scuds. The catching was just infrequent enough that my partner decided to pump one he'd just caught. The results were astounding. Instead of being filled up with the little size 14 or 16 scuds we'd been using, this guy had a bunch of BIG scuds in him - about 3/4" long! The biggest scuds we had in our boxes were about a size 10 which we quickly tied on. Guess what? We started catching more fish. We eventually broke off the only 3 or 4 big ones we had which slowed the catching down immediately when we switched back to the smaller ones.