Thanks everyone for the suggestions here and by email. Last week I spoke with my BMW (car) mechanic who also has 6 bikes. He suggested using liquid motorcycle tire balancer and sealer (RideOn.) I ordered it from Amazon (note that you may need more than one bottle based on your tire size – calculator at the RideOn website.) Cost is $28 for two bottles and they arrived last weekend. I filled the rear tire as per the recommendation, and also did the front as I had enough left over. Seems to have done the trick! No perceptible pressure loss over the last few days. Pretty pleased with this solution and not having to replace a tire with <1000 miles on it.