FET input op amps
I TOLD you I was late in getting in my reply ....
Well, I WAS going to suggest the LF356, another pin-for-pin compatible with the 741 with FET inputs. I suggested the LM310 and LF356 just because I have lots of them and use them all the time. Of course, it's the same way with the 12AT7 and 6AL5 with me! Any FET input op amp should work, just tying the inverting input back to the output to create a unity gain amp. And as Ron said, you can't run an op amp, even a FET version, open circuit or it'll go floating off into never-never land and lock the output up to one side of the supply or the other. The 10M ohm resistor he suggests will work wonders on a FET input amp. Just run down the description column of the Digi-Key catalog and pick a FET-input op amp and it's not likely you'll go wrong -- just watch out that you don't select a SMT package if you need something with thru-hole technology!
Dean