I'm looking to emphasize the reasons to support Israeli businesses. Would it be correct to add that it is a Mitzvah?
The reason that supporting Israeli businesses can be seen as a mitzva is that there is an overall mitzva to buy and sell preferably from Jews (when you have the choice) -- as mentioned by @hazoriz above. This is based on a verse in Vayikra to sell "to your fellow" which Rashi understands to mean your fellow Jew.
So if faced with the choice of buying from anyone or buying from Israel, it is more likely that buying from Israel will help you with the above mitzva. If the choice is between buying from a Jew abroad or from Israel, you can argue that when buying from Israel you help more Jews (i.e., those involved in the production, transformation, distribution of the items assuming they are manufacturing in Israel).
See here for more details.