I have some photos that I could share with you.
I'm working with Lance Cuenca who is an excellent welder and machinist
in Sunnyvale, CA.
He makes battery boxes out of sheet metal - either steel or aluminum.
He can do any size or shape you need.
He made a wedge shaped battery box for the eeVeeMotors.com Honda Civic
conversion.
That box holds 51 of the 90 AH ThunderSky Lithium cells.

He also made a box that is a combination of a wedge shape and a
rectangle for a Honda CRX conversion.
That box holds 37 of the 160 AH ThunderSky cells.

Both of the above boxes were made from steel sheet metal and have welded
corners.

He is now working on a rectangular battery box for Simon Saba's X-Prize
EV Roadster made from aluminum sheet metal.
Lance is out of town for a few days.
I think he will be back around Oct. 5th.

If you want to do it yourself, you could probably use angle iron and
sheet metal and bolt it together.
Mike Brown of Electro Automotive uses angle iron and sheets of plastic.
He welds the angle iron and uses a plastic welding technique for the
rest of it.
His boxes are designed for lead acid packs so they are probably the
wrong size for your Lithium Cells but the basic idea will probably work
for you.

Adios,

Jerry Pohorsky
Electric Auto Association
Silicon Valley Chapter President