I looked at these in the lee valley calipers in the catalog. They might
do the ticket.

I may have to hold off because my cash on hand took a beating during
christmas

Joe Fleming wrote:
William,

I have both small and large Lee Valley Veritas calipers. They are my
favorites. You can make your own, however, by bending up a stiff coat
hanger or 1/4" copper tubing. With these, you can get into any shape
you need by rebending the wire/tube.

- Bend the wire into the desired shape but leave a xx" gap between the
points. I typically have mine set to 1/2".
- Move the caliper into the vessel. Touch the inside point to the
inside surface.
- Measure (or visually measure) the resulting gap between the outside
point and the outer vessel wall. If the wire gap is 1/2" and yo see
1/8" on the outside, the wall thickness at that point is 3/8". As the
wall thickness gets thinner, the visible gap gets larger.
- Always use a calipers (homemade or store bought) such that the points
measure perpendicular to the vessel wall at the measurement point. If
you measure at a diagonal, you will get a false reading that will cause
you to think the wall is thicker than it really is.
Joe Fleming - San Diego