Sealed gear cable housing...?

esuhl

I have a mountain bike with partially exposed gear cables running along the top-tube.

I find that the gears typically shift well (as everything is well-maintained), but every so often I wash the bike and presumably get some grit or water into the gear housing, causing shifting problems.

I'm just about to upgrade the rear derailleur and replace the housing and cable anyway... But then I wondered about getting some sealed cables to stop grit getting in when I wash the bike.

I came across this review or the Yokozuna Reaction cables, and they sound great. But the kit includes brake cables (which I don't need), and it doesn't look like you can buy the gear cables separately. And there are hardly any online vendors selling them anyway...

http://www.bikeradar.com/road/gear/category/components/brake-cables/product/review-yokozuna-reaction-47814/

Anyway, I just wondered if anyone else had switched to sealed gear cables and how they found them. Any recommendations? Any good places to buy Yokozuna cables?

Cheers all :-)