The clutch cable on the DT just broke. 
I am struggling to find a replacement specific to the model.
The outer on mine is 118cm long. Are there any cables from other models that I can use?

So I did a few google searches and was able to find a few cables on ebay and also located one nos in UK. Prices are a bit stiff, but if you need it, find the lowest cost one and buy it if price matters. Really sad to see some of this stuff going for crazy prices. Sign of the times and availability. Personally if it was my bike I would contact Motion Pro and see if they could or would quote to build one for you. I had them build a tach cable for me some yr's back for my DT250A and it was a perfect fit and is servicing well. 9 yr's now. Good luck with your search.

If I recall correctly, you can fit the one from the DT250/400 (1975/76) if you're prepared to compromise on the routing - I think that this later cable is a tad shorter.

If ya desperate to go riding & it broke at the nipple at the top end then try one of these.
www.carbuilder.com/uk/solderless-nipple
If you have soldering capabilities the here's some options.
www.venhill.co.uk/cables-and-components.html
www.carrotcycles.co.uk/control-cable-par...pples-/imperial.html

Thanks, I'm looking for new if possible. I will reach out to motion pro if I can't find other alternatives. 

So im seeing 2 different part numbers here. If you use Babbitts diagram you'll see under #33 part # 363-26335-00 which i see some on ebay under that number. If you go into the tech library, parts list here on the site you'll see listed under #27 Part # 438-26335-00 which on ebay you will see new ones for around $100.
Then you have the ones where they say "it fits" for around $20 but we all know how that goes. Years 74-76 DT250/360 and 400 should use the same clutch cable but you would have to cross reference the parts numbers to be sure.

Pretty sure that the 1974 was a one year only part number and it is the one starting 438.

As per my previous post, the 1975/6 can be used, but correct routing is compromised (I think the later part is a tad shorter).

I built a DT250 rat bike with a 75 frame and 74 motor and used a Parts Unlimited clutch cable Part # K282531. Keeping in mind that the bars I used were lower than stock and it works well.

Did the cable change from pulling under the motor to pulling from the top. Actuator changed sometime but not sure when.

The cable end fits in to a boss that is cast in to the case ahead of the clutch lever actuator arm. On my 74 / 75 and probably the 76 there is no other option for the clutch lever to be operated. The clutch cable follows the Lh down tube and proceeds to go under the motor right by the exhaust pipe.