Any place to park a trailer for a few hours in bend Oregon

I'd say a Walmart or any other large store with a big parking lot. They aren't going to make trouble for a couple of hours. Cracker Barrel and Bass Pro are other possibilities.

Where are you going to the tournament? Big Sky Park? When?

If you are active at a local church, ask your pastor, minister or whoever runs it, Chances are they know a leader of a church in the area your going to and can easily get you approved for a couple hours parking as long as its not during any services.
The same can also be done often with some organizations, VFW, Moose etc.

Local Walmart is the goto. But check if it's not also congested and park at the periphery.

Saturday morning, SkyView middle school

In the old days the August Soccer tournaments were spread out all over Bend and consisted of multiple games ... and if that's your tournament your going to be there more than a few hours. If so - consider staying at one of Bends private RV parks (expensive) or maybe La Pine State park is about 1/2 hour south. Hope this helps.

Lowes home center on Cooley has a large parking lot, about 2 miles away. Have never seen that parking lot full.

Just passing through, we are on way to Crater Lk and will only see one of my daughter games. Wife staying til Sunday. Everything including the expo center had been filled for quite a while. I'll check out that Lowe's. Thanks!

No Bass Pro Shop in Bend, thank goodness! There is a Wal-Mart on 3rd st, at the south end of Bend. Lowes, at Cooley and Hwy 97 at the north end of Bend works, too.