I bought one of these from Argos and wasn’t expecting much but I found it kept bait frozen for a long time with a couple of ice blocks in there.
Although I think I paid £14 a few years ago but it’s showing as £30 now, and out of stock too
As said, nothing will keep it frozen forever, but I’ve had this in hot sun and the bait has stayed near frozen far longer than I expected.
I find electric coolboxes a mixed bag. Yes they work, but they only lower the temp by a certain amount below the external temperature. Think I read seven degrees somewhere. I froze some worms in one on a night when the temp dropped to 3-4 overnight after a mild day - wasn’t happy when I went to get my bait out the next morning!
They also need to be primed with a couple of ice blocks otherwise they take forever to lower the temperature - good for camping if you can leave one running off the site electric hook up all day.
The other thing of course is it would be an absolute ballache to lug one fishing unless you weren’t walking far.
Best advice I can give is make do with a cool bag with ice blocks in, that has a strap to sling on your back, and only take your bait out the freezer just before you leave.
Also seriously consider what bait you’re taking!
In my experience certain baits work at certain venues for particular species.
So if you’re after ray, say, take a pack of sandeel or as many as you think you’ll use, but consider that properly - if it’s a five hour session, how many casts with sandeel will you have in those hours? 20? So two packs, but I bet you’d still have half a pack left over.
I’d probably take one pack - it takes a long time to have 10 casts!