Honestly, it's a completely different thing, but I've had the craftbattery power pack for the tx500 for a couple of weeks. So far I'm happy. It may be less robust, but it has more capacity, and it's half the price, might be worth a look. Happy to answer questions.
https://craftbattery2.wordpress.com/2022/12/12/exellent-battery-for-transeiver-lab599-tx-500/
Jim
