Equivalent X27EPR-U9 spark plug for 914

I am in the market for some spark plugs for my X27EPR-U9. (My mechanic dropped one a small distance (~30cm) and reused it. Since the plugs were out, I've now had two issues shutting down the engine where it kept running. This could be because the plug was dropped, or it could be because of using anti-seize instead of thermal paste. Doesn't matter, I'm doing both.)

I'm having trouble sourcing the X27EPR-U9 locally. I see that there are, in theory, equivalents, https://www.sparkplug-crossreference.com/convert/DENSO_PN/X27EPR-U9, but it's unclear which NGK is the actual right one. 

In https://www.rotax-owner.com/en/912-914-technical-questions/4354-914-spark-plugs, a poster mentions "ND X27EPR-U9 or the NGK equivalent", but doesn't specify which is the equivalent.

And, out of curiosity, are these identical equivalents, or "pretty close to" identical? I don't know if the u-groove is all marketing, or if it actually somehow matters for the 914.