Are you aware of the "enFlow" IV fluid and blood warmer? It advertises itself as palm size and "delivers fluids/blood at a continuous 40-degrees C from KVO to 200 ml/min". It is dry heat and "can be placed close to [the] infusion site to minimize heat loss". It is "low cost". (Quotes from the magazine advertisement for it.)
http://www.enginivity.com is the Web site for it (it is made by Enginivity LLC).
Didn't know if you all knew of it yet or not. You can get a free trial of it, but I don't know if that is only for people who got the magazine mail-back card or not - you can probably call or e-mail and ask.