Speaker Mounting Brackets

[EQ3282]

I did a search, and wasn't able to find anything (aside from TV mounting bracket posts).

I need to mount my two rear surrounds on the crossbeam supports in a finished basement. I have the Polk RM6750's, each weighing 2 lbs.

Can anyone recommend some good mounting brackets? I've found a few for sale, but some seem to be cheaply made (flimsy plastic used in plethora), while others are too ambiguous to jump on or quite expensive for the purpose ($30+).

Budget is fairly open, though keeping it on the inexpensive side ($10-20 per bracket) is preferred.

Thanks in advance!