These folks have the Tivax in stock at a good price and the Artec Pro.
The Artec is 12vdc and the Pro has buttons on top.
This is the only place to get the Pro currently.
They don't have many.
The only difference between the Pro and the standard 3A or 3AP is the buttons.
The standard Artec is available here.
They have the Tivax at a higher price and the Pal refurbished.
The Pal and Pal Plus have the extensive guide.
The Pal Plus has the better tuner.
Any dc powered box may be used on batteries, but the Artec is confirmed to work on 12 vdc and has a decent tuner.
It is in demand for RVs currently, and emergency systems.
There have been different versions, but the last LL model with a better guide is considered best.
These are useful in storm or other power grid down emergencies.
And of course, any box may be used with an inverter.
Beware of ground conflicts on tvs with other equipment.
If anyone is interested, I can post links to approaches to standby power setups.
AVS Forums is still the best source for general info.
Tiger direct still has the Access box and some radio shacks have some.