Yeah along the lines of what has been said, a company should usually have a philanthropic aid director. If you can give that person a call and talk with them about your team they may just like you enough to put you in the budget for next year (not exactly quick money but next year it will help).
Call up every company in the area, there is no harm in at least asking if they have any scraps to donate to a high school robotics team
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Also try asking some teams at the regional for a contact. BMS, NASA, J&J all sponsor tons of teams and I am sure each team has a contact to these companies, among other.
The grocery store idea sounds good for quick cash on a Saturday morning or something. You can impress all those impatient kids that are dragged to the store with their parents every week (thus planting the seed early).
Let us know how things work out.