I've found another cheap replacement cable for HD700. I was looking for something light and short for portable use. The cable I knew about before was Sennheiser 083380 and I was going to order that one, cut it to about 1 m and re-plug, but yesterday I noticed another one in a store. It was very cheap so I bought it without testing - and it works.
The cable for Krüger&Matz KM660 and Krüger&Matz KM665 headphones fits without any adjustments (tested - that's the one I got), cable for Krüger&Matz KM0830 will probably fit too (not tested, but looks like the 2.5 mm mono jacks are thin enough).
Krüger&Matz is a Polish brand, but their products are made in China. They have headphones, speakers and other electronics. They sell replacement cables separately in Poland. Not sure if these cables can be purchased separately outside Poland, but Kruger&Matz has distribution in Romania, Switzerland and Benelux and they do sell headphones there, so it could be possible at least in these countries.
Edit: Krüger&Matz headphones are made by Esmooth (Chinese OEM) that also makes the same exact headphones under its own brand and for the brands Meze, Senta, Hores, Symphonized, BearBizz, Zagg, Tribeca (those I know about, there could be more), so cables terminated with 2.5 mm mono jacks for any of these brands are probably the same.
The cable is 1.2 m, 3.5 mm jack on the source device side, thin 2.5 mm mono jacks on the headphones side. There's also a version with microphone, I got the one without. The cable is in nylon braided sleeve (so probably a bit microphonic), rather thin, probably not very durable. But it's pocket-short (unlike the other possible replacement, Sennheiser 083380 cable for EH250, EH350, HD212 Pro, HD477, HD497, which is also thin and flexible, but 3 m long), light, flexible, and the best part is the price: $5 for the cable without in-line mic, $6 for the cable with mic.