From the Panasonic line, it doesn't get much better than the 61's. Many years ago I would use the WM-60AY's which were lower sensitivity; I really liked these. Then there are the Panasonic capsules being used in Sonic Studio mics. I've never been able to pin down the exact model, but they're much older and much much lower sensitivity than the current 61's. I think Leonard purchased a batch of 5000 of these right before they were discontinued.
Aside from trying different capsules, have you experimented with the Linkwitz modification? This involves severing the existing trace between the capsule and the negative solder and creating a new trace between the capsule and positive solder pad. Accompanied by a reverse polarity battery box, this modification results in lower sensitivity and (supposedly) more linear response. This is the same modification used in Coresound Binaurals.
In the past, I have tried many non-panasonic capsules mostly purchased through digikey, but none have been close to the final quality of the modified 60ay/61a capsules.
Topic: DIY'er replacing WM-61 capsules - accepted replacement? (Read 15556 times)