His eminence, Āyatullāh Hadavi Tehrani’s view on the matter:

With attention to the danger posed by Zionism to the Islāmic world, in fact to humanity, any action that results in the strengthening of this despicable movement is absolutely forbidden. With this in mind, buying and selling products that in any way help strengthen Zionism is impermissible, except in cases where it is necessary, only to the extent necessary. It is upon the duty bound (mukallaf)  to specify such cases. Although, if it is not proven [that they support Israel], there is no objection [in buying or selling such products].