Vin,
When I looked ............. and looked ........... and looked some more ............
The best I came up with was D cell Li Ion single cells with a 10A capacity, as with most single cells they were 1.2V, so you'd need 10, the cost of those was very close to £100, then you'd need to make them into a pack, not that difficult to do but you need to be very competent and confident with a 100W soldering iron, I learned many years ago through making battery packs for models cars/boats and recently with Li Po packs for big model Helis.
It's really easy to ruin a cell with excess heat,