Have a read through this recent thread as my original ( 10 year old Panosonic) was fine one week and then after a cold snap Click,Click,Click...the Bosch S4 that I got in the end was a tight fit inside the plastic shroud but it does fit.
Don't forget you will have to reset electric Windows after battery dis-connect.
https://www.lexusownersclub.co.uk/forum/topic/107731-best-12v-battery-for-is250/
Paul m.