The battery is 12.5 volts this morning, after a short drive yesterday morning and charging the day before that, so it might survive awhile longer. I think the 92-00 Civic battery is a 51R. A post
here suggested a group 34, but that is too big for the space in my car.
Group sizes & dimensions
51r ~ 9.38" L ~ 5.13" W ~ 8.88" H ~ 425 cca / 85 reserve capacity OEM
34 ~ 10.25" L ~ 6.81" W ~ 7.88" H ~ 800 cca / 110 reserve capacity
Size & dimensions with cca & RC
Costco's 51r is 500 cca so I'll get the same one again, unless a larger battery will fit in the space.