Hi Don,

What you need are low temperature coefficient resistors not specifically low tolerance. The two however, do tend to end up being together.
Also if you are using a voltage divider setup with two resistors it might be an idea to mount them very close to each other and also drop a blob of epoxy or silicone over them both so they are thermally linked.
This way whatever factor affecting one resistor should affect them both together and negate most of the variation.
Alternatively use one of those resistor networks, they are all in the same plastic can, thermally associated with each other, manufactured with the same machine, chances are theyre pretty tight.

A quick look through the farnell catalogue reveals some nice +/-.1% 10ppm/deg c resistors.

When you think that some standard resistors are 700ppm/deg c you quickly realise why they shift around so much.

Hope this helps.

Regards

Darryl..