Clamp or something for stability between two steel beams

Hi, I trying to put a frame up made of 75x50 RHS. There’s two uprights bolted to the floor and a crossbeam over the top about 3m high. The middle of the top crossbeam is about 200mm from another vertical pole that I’m hoping to secure the frame onto for horizontal stability only - not to bear weight. It’s just to stop the frame for leaning forward or back.

So I’m looking for an adjustable double sided clamp thing to clamp onto the crossbeam of the frame and the pole. Something that has clamps on either side that can be tightened or loosened. And the distance between the clamps can be shortened or lengthened up to a max as required. I don’t want to drill into the pole (but into the frame is ok)

I feel like this thing is obvious and exists off the shelf but I can’t find the search terms that suit what I’m looking for - any ideas please tell me! Or if there’s something simpler please let me know…

Thanks

Regards, an EE