I would agree with swede, another pump might be the best option. User "Pol" has instructions and a part list for what he used as a "stirrer" in his 2 cooler e-herms set-up.
post #34 and #35 have the parts list. He ordered his parts from mcmaster-carr.
I decided to go with a cheaper second pump from greatbreweh.com over the stirrer. However, I ordered it 3+ weeks ago and still haven't received it AND they haven't responded to my e-mail. So, I'm not sure if this is good advice either. The pump they sell is about 50$ cheaper than a march or chugger and looks like it can do a damn good job. Just note the customer service from greatbreweh has been subpar for me as well as for others from what I have read.
I hope this helps,