[Closed] Hope Vision 1 - rechargeable battery pack?

I'm thinking about giving some night riding a go.
Got a cheapy cree bar mounted with separate battery pack job of amazon, but wanted something for on the helmet as well.
Then I remembered I have a Hope Vision 1 from when I commuted on the road bike a few years ago.
However, it has a battery holder that takes 4x AA batteries. I used rechargeables and had a spare holder. But, as technology continues it's relentless march I was wondering if there was a one piece rechargeable unit that would fit in the same space and do the job.
I can't find anything online, but other than random searching I don't know if there's a standard generic unit that would fit in that's not Hope specific?
Anyone within the STW Hive a battery sizes expert?

For reference, this is the holder:
[img] [/img]