Need to replace vibe. pump on a Expobar Office, any recommendations for a vibe. pump that would be upgrade from the stock one?

Pretty much all vibe pumps are the same, so there's not really an upgrade. The Fluid-O-Tech ones are supposed to be rated for commercial usage, so that might be considered an upgrade. However, all of them are going to provide ~15 bar pressure.

You might want to consider upgrading to a rotary pump. But if you want to stay with a vibration pump, a Cimbali vibe pump would be a good choice. Most espresso vibe pumps are only rated for intermittent duty and will often fail after 2 - 5 years of service. The pump used in the M21 (Cimbali Junior) is a true commercial vibe pump that is rated for continuous duty. It's somewhat more expensive, but will typically outlive most brands several times over. Fluid-o-tech is a well known brand. If the fluid-o-tech is also rated for continuous duty, then go with whichever one costs less.

And if you're replacing the vibe pump anyway, you might want to mount it outboard e.g. in a cabinet to eliminate most of the vibe pump noise.

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Thanks for the info, I will check out the Fluid-o-tech.

Have a look at this:

Expobar Rotary Conversion