I'm not actually clear on whether or not you are looking to make an infinite phaser, but I was kind of blown away that I'd never heard of this before, so I looked into it a bit.
I spent some time going through Bode's patent for the Barberpole Phaser (or, at least, I think this is the patent for it). The quadrature LFO is just part of the frequency shifter itself. In fact, while it gives a similar illusion, it's not really even designed like Risset's infinite glissando at all (fun fact: that was actually the first thing I successfully made in Pd). The infinite glissando essentially works like acreil's suggestion, in that you have several oscillators that are being windowed, and they are gradually changing in pitch relative to the phase of the window. I tried applying that idea to a flanger (easier to make than a phaser), and I didn't find it particularly convincing.
So I looked at the patent, and it works quite differently. Basically, you send the input through a series of all-pass filters (or a short delay-line for an infinite flanger). Then, you send that signal through a frequency shifter. When you sum the wet and dry signal up, the notches continuously go up or down (depending on if you shifted it up or down) in one direction. The amount of the frequency shift determines the time it takes for one notch to go from min to max.
Now, it's not outright said in the patent, but this is what I think is happening: it's a very novel way of using beating. When you add two sinewaves that are only 2 Hz apart, you hear volumn fluctuations at 2 Hz. In this case, all of the frequencies in the dry signal are shifted by the same amount in the wet signal, so they beat at the same frequency. It just so happens that the phase shifts of the all-pass filters make the beating controlled, so that the notches end up flowing across the spectrum at the rate of the beating. That's my guess, anyway (and I have no idea if that was even clear).
The attached patch is my attempt at making an infinite flanger using this method. [hilbert~] and [complex-mod~] combine to make the frequency shifter. To make this a phaser, just replace [cyclone/comb~] with a series of all-pass filters.