Lithium batteries that fit safe-light flashlights?

[passive101]

Energizer lithiums do not fit in the lights. They are square and not rounded on the edges.

 

[Shadowww]

Ultralife 9V Lithium, perhaps?
http://ultralifecorporation.com/be-commercial/products/9volt/u9vl-j-p/

Judging by this pic, they have rounded edges:

 

[passive101]

I was told these would fit if take off the foil. How hard is that to do?

 

[Shadowww]

Providing you have got suitable tools (pliers would work, for example) it's easy and fast process.