I always keep at least one Audio-Technica AT8202 in my bag. I've used them on my hydrophone and even the MKH50, and I can't hear much (any?) additional noise. the AT8202 is switchable betweeen -10, -20, and -30 dB; pretty darned spiffy.
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+1 for the Shure A15AS, been using those for years without a hitch.
In answer to your cheaper pad question, make sure that if you use an off brand besides Shure or Audio Technica that it has a good following. I've made mistakes in my youth by chincing on cheaper gear that ended up costing me more money and time in the long run.
When I worked at Electric Lady Studios, we used the Shure A15AS barrel adapters. They didn't effect the signal noticeably (except for the expected padding of course...), and are switchable, so you aren't stuck with a certain value.
A 5-pin stereo pad would be sweet, but I've never seen one before. If they make one, that'd lighten your load, but would also limit you to using it with your 418s (nice mic, btw).