12v Battery Problems

Two weeks ago my 2008 prius would not start (not the first time this has happened). This time when we tried to jump it, we got an error about it being abnormally parked. Apparently that's a pretty typical sign of a failing battery. We tried to get it replaced and at the suggestion of this forum we went with an Optima Yellowtop. However after we pulled the original battery, we found that the Optima was a couple of inches too long. No worries, we just took it back and tried to get another battery, however every battery we found that was in stock around town was too long to fit in our prius. Something seems off here and I really need help.

We found a battery outfitter nearby that claimed they've seen this before, but didn't have any in stock and have been on back order now for 2 weeks. Has anyone else ever had this problem before?

Our current battery (which I'm assuming is OEM) is 7wx5dx8h, but every battery we've been able to get our hands on is at least 9-10 inches long and there is no way we can get it to fit. Any advice?