When I was at the annual Quartzsite RV event 3 years ago, one of the vendors there was Brazels RV. They are based in Washington state I believe. In their booth, they had a replacement fan for the C-7 and others and I THINK they had one for the 3126. But, I'm not sure. It was/is a stream lined version that was supposed to cost less horse power to run and, cool better. It was not cheap though. I don't remember what the cost was but, it was not attractive enough for me to make a move on one. But, in any case, if you cannot find a bone stock fan for your 3126, you might try Brazels and see if they have an answer for you. Good luck.
Scott