Buy one that looks good, and also buy a bastard file. I gave up hope on finding a wrench that fits all my #11 guns. My current favorite that I carry with me in my pocket everywhere I go has a deepened notch, a narrowed end, and one bar of the T-bar cut off. That's what it took to make it fit all my guns. Yep. The tbar rubbed the hammer on the first and last twist for the nipple on my gpr. Cut one side off, and no longer any issue.
The wrench was too thick to fit in the cranny between nipple and barrel on my single shot pistol. So had to narrow the outside of the wrench. And also deepen the notch for a better fit.