Got lucky in that my brother was in the mood to help me get my bike to the shop up in Pasadena. The flat seems to have been from the Mr. Tuffy liner. That's our best guess, anyway. The hole was *right* where the tube had a seam. Bike shop suggested that if I really wanted to avoid flats I should upgrade to a Schwalbe Marathon. The cost to do that is about 12 times what merely fixing the flat would be. OTOH, constantly having to hassle with punctures or having a flat happen while I'm in the middle of nowhere would be disastrous for me so I'm ponying up. At least I can do it now. I think if I were to wait on it, putting it off for a time where I may finally be living by myself again, I might not have room in the budget. So better to do it now.
ETA: It's a good thing I bought an LA County Bike Coalition membership. They have an LACBC discount at this shop and this is a prime example of when that comes in handy. The discount is 10% off parts.
It's another gorgeous day. Purple mountain majesties - we haz them.