I don't see a problem with just using the 535 itself. I've been sweating on mine for years now without “much incident”. Shure will replace the cable for $16.
I say “much incident” because I did have that sound-out problem last year with one earpiece on the 535. However, now that I know to remove the earpiece occasionally and use a connection-cleaner to prevent corrosion (from sweat, no doubt, seeping in) between the earpiece and cable (it's all good).
Cleaning the cable daily after sweating on it is a must. Every work day I wear my 535 while loading my truck and every day (even on cold days) I sweat. I sweat profusely (I'm a heavy sweater) yet my clear cable is still clear after years. They say it is inevitable that it will turn green from body oils but not if you clean it daily (at least in my experience). I carry a bottle of those disinfectant wipes and I usually give it a once over after I stop sweating and again at the end of the day.
I have an old Shure E5c (clear cable) that's still clear also. I use to jog with it daily between 2004 and 2007. After the jog I would use part of a paper towel and a dab of dish-washing liquid to wipe the cable down. Then I'd rinse it (using my hand to cover and keep the earpiece and the crossover in the Y-split from getting soaked). I would use a moist paper towel directly on the earpiece and Y-split crossover.
You can buy an extra 535 cable and some extra foam tips. I do have a modified triple-flange tip with one of the foam tips attached to the stem. I dip it in hydrogen-peroxide (every now and then) and let it dry in a box with Silica Gel. I mostly just use the triple-flange by itself and I clean it daily with hand soap.
If you think water has gotten thru the nozzle and inside of the earpiece of the 535 itself, you can store it in a box with one of those Silica Gel packs (overnight). It'll be fine.
Once you've had time to get over the fear of destroying a valued property, you'll find that it is really hard to tear it up without a hammer (or getting hit by a car on your run). Just run the line under your shirt and around your ears and clean it daily.