spit rod

Why not go to your local metal dealer and get some 1" or 2" steel round bar or square bar.

That's what I would do. I made one once from a chrome rod I bought at a motorcyle swap meet. It was an old extended springer front end. Any steel would work as long as you keep it oiled to retard rust.

Spit rods for a 100 lb pig need to be pretty stout.
The longer the spit the thicker it needs to be.

The one I saw that was homemade was 1.5" x 1.5" square stainless
and the length was in the area of 4.0' long.
He usually cooks 80 to 100 lb hogs.

Where he got the rod from is another question.

I would think any place that sells metals.
Like this place.
http://www.mcmaster.com/

EXAMPLE:
Here is a 6 foot piece of 303 stainlees hex 1.5" for $196.00

Metals > Shape > Length > Hex Size > Compare Items



Stainless Steel
This product matches all of your selections.



Part Number: 89665K92 $196.00 Each
Material
Easy-to-Machine Stainless Steel (Type 303)
Finish/Coating
Unpolished (Mill)
Shape
Hexagonal Bars
Length
6'
Length Tolerance
±3"
Hex Size
1-1/2"
Tolerance
Oversize
Material Certification
Without Material Certification
Condition/Temper
Annealed
Hardness
262 Brinell
Yield Strength
35,000 psi
Specifications Met
American Society for Testing and Materials (ASTM)
ASTM Specifications
ASTM A484 and ASTM A582

http://cgi.ebay.com/304-Stainless-Steel-Square-Bar-1-x-1-x-48_W0QQitemZ120001837921QQihZ002QQcategoryZ117510QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/416-Stainless-Steel-Hex-Bar-750-dia-x-48-long_W0QQitemZ110001912862QQihZ001QQcategoryZ117510QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/STAINLESS-STEEL-ROUND-SOLID-1-1-2-DIAMETER-71-LONG_W0QQitemZ300003154675QQihZ020QQcategoryZ117510QQrdZ1QQcmdZViewItem