A non threaded barrel may be necessary to comply with local gun laws IE in Manhattan, NY.HK Webshop has USP 45 barrels.
Do you not like the TB? I'm sure I'm missing a few things, but a USP 45 "Tactical" is a USP with a threaded barrel, adjustable suppressor height sights, match trigger, and TACTICAL engraved on the slide. Assuming you're not CC'ing it, not sure why you would want a standard barrel on there.
A slip-on rubber grip would be your only option, and it would be fat.
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