12v battery is dead, what else can I use?

yes, pretty much everyone offers an option. get the cheapest you can find, they're all decent.

BUT, beware, you have it backwards. sks is the larger battery, non sks is smaller.
the smart thing to do would buy the cheaper battery, and if it happens to be the larger, you can change the holder.

 

You might find a toyotadealer inyour area who will do you a good price. Cant hurt to ask. Im 40 miles from WI state line, found $55.00 cheaper in wisconsin.

 

I found $160 online AGM Toyota Prius Auxiliary Battery | Prius 12V Battery

If you have a NAPA auto parts, they should have the correct battery for $186.
https://www.napaonline.com/en/p/NBE9851P

 

I dont know about that one, i decided (on mine to stick with oem) personal preference.

 

The Toyota battery is the best battery; if for no other reason than a 84 month warranty.

I was finding cheap batteries that fit, just so he did not build some Franken-battery he would regret forever.

 

@PriusCamper uses a wheelchair battery that is quite inexpensive. He hasn’t been around lately. If you search his name you might find out how he did it.

 

Also (cost about $100.00) but a good desulfating charger (i have optimate 6) can oftentimes recover a battery we think is no good. A good recovery charger is a good thing to have for all your vehicles. Keep in mind the old adage in relation to chargers and most things "u get what u pay for", cheep is as cheep duz.