Hallelujah! I located rye flour today at a store within reasonable driving distance! And not just simply rye flour: I can get wholemeal rye, medium rye and crushed rye. Thanks MiniO for one of your tips; I went to the mill's web site, looked at their list of stockists (for the Americans, the equivalent would be retailers), and finally made it to the store today. For anyone else in the Pretoria (Tshwane) area, it is the SuperSpar store at the Silver Lakes shopping center, just off Hans Strijdom Drive.
I decided to slowly work my way back into baking with rye and limited myself to a bag of medium rye (which I had already wheedled from the baker before rounding the corner of the aisle containing flours - oh me of little faith).
Since I had pulled my starter out of cold storage last evening and given it a feeding, I nipped off a tablespoon or so, stirred in some water and enough rye to make a thick paste. It's sitting on the counter now. With any luck, the party for the lacto-, aceto- and yeast-beasties should be revving up.
I noticed that the gluten in the starter was almost completely destroyed, so I took a taste and was surprised by the intense acidity. I think my starter may be longer on bacteria than on yeast, so I'll try running it closer to 100% hydration for a while (it's normally kept at 50%) to see if that favors yeast development and gets things into a better balance between leavening and flavor critters.
Color me happy!