Trade and Commerce
Official Weights (primary)
In the forum at Pompeii (in a niche outside the Temple of Apollo) a limestone table was found containing an official set of weights and measures against which market goods could be tested. (Mensa Ponderaria).
Similarly, in Herculaneum we know from inscriptions that they also had an official set of weights.
These tables would have been to the Roman standard. On the Pompeiian table an inscription was found saying:
"Aulus Clodius Flaccus, son of Aulus, and Numerius Arcaeus Arellianus Caledus, son of Numerius, duumviri for the administration of justice, (set up) the equalizing measures by decree of the decurions." CIL X 793
With this you could argue to pieces of primary evidence in favor of both trade and commerce. e.g. The weights being to the Roman standard could be suggested to imply that foreign trade with other parts of the Roman empire occurred.
Fullers (Primary)
Fullery of Stephanus (fullonica Stephani) was found in Region I of Pompeii by Spinazzola.
Vineyards (primary and secondary)
The physical remains of the vineyards bares testament to the idea that wine and grapes where produced and sold within the region. On the other hand, you could argue the idea of Wilhemina Jashemski's vine root plaster casts was secondary evidence....actually your probably couldn't use that...you could use his findings from the plaster cast as secondary evidence.
Theres heaps of others that could be used for this. Eg. Bakeries - evidence of large ovens, grain mills. Wine production and Olive oil - large marble wine and olive presses have been found.