I'm planning on (dreaming about) putting together a HERMS. Appropriate pumps have seemed expensive, now that all of my student loans are now due. I found this, and it seems like it would be great. It's only a hand pump, but it shouldn't be too difficult to motorize. That and it's cheap. Amazon has it available at something like $6-7. The inner tubing is replacable, which is great, because it's designed for radio control airplane fuel, and I wouldn't assume it's food safe. But, a little silicone tubing, and it seems like you'd be in business. One potential drawback is that it says the ideal pumping speed is 60 rpm, and that 1 revolution pumps 0.6 oz, which equates to a little over 1/4 gpm. This seems slow compared to what little I know about HERMS. But, maybe their "ideal" is low, and I could just up the rpm's and see what happens? That and they're marketing to folks who are used to moving smaller volumes, so they've had no incetive to brag about moving 1 gpm. The difference in tubing flexibility and/or diamter may make a difference as well. I'm thinking that for the price, if I can't get it to work, I've still spent less than I would going to a movie.
http://www.dbproducts.com/downloads/pdf/ss_tech_sheet.pdf
http://www.dbproducts.com/downloads/pdf/ssgl_manual.pdf
http://www.dbproducts.com/downloads/pdf/ss_tech_sheet.pdf
http://www.dbproducts.com/downloads/pdf/ssgl_manual.pdf