Probably a good idea to phone Chris at Jungle Junction, who keeps a stock of tyres, and the KTM dealer in Nairobi, ditto. Contact details easily found on the HUBB.

For what it's worth my daughter and son-in-law just left Nairobi for 5 days in the Maro and will return at the weekend. She found Mitas are available there but only the motocross type, more air than knobbles. So has bought Vee rubber at JJ's.
I bought a Vee rubber there last year and it lasted easily to Cape Town (N - S journey). But suffered a small split on hitting a rock hard in Namibia. It was a worry at first but got me to S. Africa OK.

If you're interested, they both will be leaving Nairobi again in August to ride to Khartoum and would prefer to ride with others. Timing will be to have a steady, ie. not hurried, journey to arrive in Khartoum 1st week of September.
Their situation is the reverse of your's, she being the experienced one on bikes, he, less than 6 months experience before starting their journey, so could be interesting to link up. Also they rode from Khartoum to Nairobi (me as well) last year so know a little of the route. Especially Roberts Camp, N. Kenya, where the hippos roam and munch among the tents at night - quite a highlight! (Saw your note in your blog)

Let me know if you're interested, will put you in touch.

Have a good journey.

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TTR250 - London to Cape Town