Per discussions I have had with a LoCo Council Member there is no problem accepting sponsorship's or donations from companies so long as such a sponsorship or donation does not come with strings attached that require the LoCo to do sales pitches or endorse a certain product or company.
Further I have talked with a few other LoCo Team Leads and it seems like accepting sponsorship's and donations is common and helps LoCo's provide common things like stickers, shirts and light food at events.
I guess a good rule of thumb is just try to make it clear that by making a donation or sponsoring an event that they are not entitled to any endorsement or perk other than perhaps a personal thanks at the event or once on the mailing list. Additionally I personally feel that when accepting donations or sponsorship's it is best to be transparent to your entire LoCo and make sure the entire team knows what was donated/sponsored.
In closing I suggest if a company is going to sponsor an expense that you ask that they directly pay for it versus accepting any monies.
Surely, if you have any questions or need guidance you can always seek out such from the LoCo Council via their mailing list or on IRC.